NATIONAL TOXICOLOGY PROGRAM Technical Report Series No. 229 CARCINOGENESIS BIOASSAY OF GUAR GUM (CAS NO. 9000-30-0) IN F344 RATS AND B6C3F} MICE (FEED STUDY) U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service National Institutes of Health
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NATIONAL TOXICOLOGY PROGRAM Technical Report Series No. 229
CARCINOGENESIS BIOASSAY OF
GUAR GUM
(CAS NO. 9000-30-0)
IN F344 RATS AND B6C3F} MICE (FEED STUDY)
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service
National Institutes of Health
NTP Technical Report
on the
CARCINOGENESIS BIOASSAY
of
GUAR GUM
(CAS No. 9000-30-0)
IN F344 RATS AND B6C3F! MICE
(FEED STUDY)
NATIONAL TOXICOLOGY PROGRAM Research Triangle Park
P. 0. Box 12233 North Carolina 27709
and Bethesda, Maryland 20205
March 1982
NTP 80-83 NIH Publication No. 82-1785
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service
National Institutes of Health
NOTE TO THE READER
This is one in a series of experiments designed to determine whether selected chemicals produce cancer in animals. Chemicals selected for testing in the NTP carcinogenesis bioassay program are chosen primarily on the bases of human exposure, level of production, and chemical structure. Selection per se is not an indicator of a chemical's carcinogenic potential. Negative results, in which the test animals do not have a greater incidence of cancer than control animals, do not necessarily mean that a test chemical is not a carcinogen, inasmuch as the experiments are conducted under a limited set of conditions. Positive results demonstrate that a test chemical is carcinogenic for animals under the conditions of the test and indicate that exposure to the chemical is a potential hazard to humans . The determination of the risk to humans from chemicals found to be carcinogenic in animals requires a wider analysis which extends beyond the purview of this study.
This study was initiated by the National Cancer Institute's Carcinogenesis Testing Program, now part of the National Institute of Environmental Health Sciences, National Toxicology Program.
These NTP Technical Reports are available for sale from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161(703-487-4650).
Comments and questions about the National Toxicology Program Technical Reports on Carcinogenesis Bioassays should be directed to the National Toxicology Program, located at Room A-306, Landow Building, Bethesda, MD 20205 (301-496-1152) or at Research Triangle Park, NC 27709 (919-541-3991).
Although every effort is made to prepare the Technical Reports as accurately as possible, mistakes may occur. Readers are requested to communicate any mistakes to the Deputy Director, NTP (P.O. Box 12233, Research Triangle Park, NC 27709), so that corrective action may be taken. Further, anyone who is aware of related ongoing or published studies not mentioned in this report is encouraged to make this information known to the NTP.
11
TABLE OF CONTENTS
Page
Abstract vii Contributors ix Reviewers xi Summary of Peer Review Comments xiii
I. Introduction 1
II. Materials and Methods 3
A. Chemical 3 B. Dietary Preparation 3 C. Animals 5 D. Animal Maintenance 5 E. Acute Oral Toxicity and Repeated Dose Studies 6 F. Subchronic Studies 6 G. Chronic Studies 9 H. Clinical Examinations and Pathology 9 I. Data Recording and Statistical Analyses 11
III. Results - Rats 15
A. Body Weights and Clinical Signs (Rats) 15 B. Survival (Rats) 15 C. Pathology (Rats) 19 D. Statistical Analyses of Results (Rats) 19
IV. Results - Mice 33
A. Body Weights and Clinical Signs (Mice) 33 B. Survival (Mice) 33 C. Pathology (Mice) 37 D. Statistical Analyses of Results (Mice) 37
V. Discussion 47
VI. Conclusion 49
VII. Bibliography 51
TABLES
Table 1 Source and Description of Materials Used for Animal Maintenance . , 4
Table 2 Dosage, Survival and Mean Body Weights of Rats Fed Diets Containing Guar Gum for 91 days 7
111
Page
Table 3 Dosage, Survival and Mean Body Weights of Mice Fed Diets Containing Guar Gum for 91 days 8
Table 4 Experimental Design of Chronic Feeding Studies with Guar Gum in Rats and Mice 10
Table 5 Mean Body Weight Change (Relative to Controls) of Rats Fed Diets Containing Guar Gum 17
Table 6 Analyses of the Incidence of Primary Tumors in Male Rats Fed Diets Containing Guar Gum 22
Table 7 Analyses of the Incidence of Primary Tumors in Female Rats Fed Diets Containing Guar Gum 28
Table 8 Mean Body Weight Change (Relative to Controls) of Mice Fed Diets Containing Guar Gum 35
Table 9 Analyses of the Time Adjusted Incidence of Primary Tumors in Male Mice Fed Diets Containing Guar Gum 39
Table 10 Analyses of the Incidence of Primary Tumors in Female Mice Fed Diets Containing Guar Gum 43
Appendix A Summary of the Incidence of Neoplasms in Rats Fed Diets Containing Guar Gum
IV
53
Page
Table Al Summary of the Incidence of Neoplasms in Male Rats Fed Diets Containing Guar Gum 55
Table A2 Summary of the Incidence of Neoplasms in Female Rats Fed Diets Containing Guar Gum 59
Appendix B Summary of the Incidence of Neoplasms in Mice Fed Diets Containing Guar Gum 63
Table Bl Summary of the Incidence of Neoplasms in Male Mice Fed Diets Containing Guar Gum 65
Table B2 Summary of the Incidence of Neoplasms in Female Mice Fed Diets Containing Guar Gum 70
Appendix C Summary of the Incidence of Nonneoplastic Lesions in Rats Fed Diets Containing Guar Gum 75
Table Cl Summary of the Incidence of Nonneoplastic Lesions in Male Rats Fed Diets Containing Guar Gum 77
Table C2 Summary of the Incidence of Nonneoplastic Lesions in Female Rats Fed Diets Containing Guar Gum 83
Appendix D Summary of the Incidence of Nonneoplastic Lesions in Mice Fed Diets Containing Guar Gum 89
Table Dl Summary of the Incidence of Nonneoplastic Lesions in Male Mice Fed Diets Containing Guar Gum 91
Table D2 Summary of the Incidence of Nonneoplastic Lesions in Female Mice Fed Diets Containing Guar Gum 96
Appendix E Analysis of Guar Gum (Lot No. A-40-F and F10-77-966-1) Midwest Research Institute 103
Appendix F Feed Consumption by Rats and Mice Receiving Guar Gum 109
Table Fl
Table F2
Table F3
Table F4
Feed Constnnption by Male Rats Receiving Guar Gum ,
Feed Consumption by Female Rats Receiving Guar Gum
Feed Consumption by Male Mice Receiving Guar Gum ....
Feed Consumption by Female Mice Receiving Guar Gum
Page
111
112
113
114
VI
ABSTRACT
A carcinogenesis bioassay of guar gum, a widely used food stabilizer, was conducted by feeding diets containing 25,000 or 50,000 ppm of the test substance from two batches having purities of 83.5% and 91.9% to 50 F344 rats and 50 B6C3F1 mice of either sex for 103 weeks. Groups of 50 untreated rats and mice of either sex served as controls. The rodents might have tolerated higher doses but 50,000 ppm (5% of diet) is the upper limit for chronic feeding studies in the Bioassay Program, and this level represented the maximum tolerated dose (MTD) for females of both species in the present study.
After week 20 in mice and week 40 in rats, mean body weights of high-dose females were lower than those of the untreated controls. No compound-related clinical signs or adverse effects on survival were observed. Feed consumption by dosed rats and dosed mice of either sex was lower than that of the controls. There were increased incidences of adenomas of the pituitary (8/45, 18% controls; 17/46, 37% low dose; 17/43, 40% high dose) in male rats and pheochromocytomas of the adrenal (0/50, 0%; 5/50, 10%; 6/50, 12%) in female rats, but these differences (P<0.035) were considered to be unrelated to administration of guar gum. When pituitary adenomas or carcinomas and when pheochromocytomas or malignant pheochromocytomas are combined, the statistical differences disappear.
Hepatocellular carcinomas (15/44, 34%; 6/50, 12%; 6/49, 12%) occurred in treated male mice at incidences significantly (P^O.Oll) lower than that in controls. The combined incidence of male mice with either hepatocellular adenomas or carcinomas (16/44, 36%; 12/50, 24%; 7/49, 14%) was also significantly (P=0.013) lower in the high-dose group.
Under the conditions of this bioassay, guar gum was not carcinogenic for F344 rats or B6C3F1 mice of either sex.
VII
CONTRIBUTORS
The bioassay of guar gum was conducted at EG&G Mason Research Institute, Worchester, Massachusetts, under a subcontract to Tracor Jitco, Inc., the prime contractor for the NCI/NTP Bioassay Program. The prechronic study was started on September 1976 and finished in February 1977; the chronic study was begun in May 1977 and completed in August 1979.
The bioassay was conducted under the direction of Drs. H. Lilja (1) and E. Massaro (1,2), principal investigators. Doses of the test chemical were selected by Drs. J. Robens (3,4), C. Cueto (6), and 0. Fitzhugh (3,7). The program manager was Ms. R. Monson (1). Ms. A. Good (1) supervised the technicians in charge of animal care, and Ms. E. Zepp (1) supervised the preparation of the feed mixtures and collected samples of the diets for analysis. Ms. D. Bouthot (1) kept all daily records of the test. Dr. A. Russfield (1), pathologist, directed the necropsies and performed the histopathologic evaluations. The pathology report and selected slides were evaluated by the NCI Pathology Working Group as described in Ward et al. (1978). The diagnoses represent a consensus of contracting pathologists and the NCI Pathology Working Group, with final approval by the NCI Pathology Working Group.
Animal pathology tables and survival tables were compiled at EG&G Mason Research Institute, Rockville Maryland (8). The statistical analyses were performed by Dr. J. R. Joiner (3) and Mr. J. Warner (3) using methods selected for the bioassay program by Dr. J. J. Gart (9). Chemical analyses were conducted at Midwest Research Institute (10).
This report was prepared at Tracor Jitco (3). Those responsible for the report at Tracor Jitco were Dr. C. Cueto (6), Director of Bioassay Program; Dr. S. S. Olin, Associate Director; Dr. M. A. Stedham, pathologist; Dr. J. Tomaszewski, chemist; Dr. W. D. Theriault, reports manager; and Dr. A. C. Jacobs, bioscience writer.
The following scientists at NTP (5) were responsible for evaluating the bioassay experiment, interpreting the results, and reporting the findings: Dr. Michael P. Dieter (Chemical Manager), Dr. J. Fielding Douglas, Dr. Charles Grieshaber, Dr. James Huff, Dr. Joseph Baseman, Dr. Ernest E. McConnell, Dr. John A. Moore, Dr. Sherman F. Stinson, Dr. Raymond Tennant, and Dr. Jerrold M. Ward.
(1) EG&G Mason Research Institute, 57 Union Street, Worchester, Massachusetts 06108
(2) Now with Pennsylvania State University, 226 Fenske Laboratory, University Park, Pennsylvania 16802
IX
(3) Tracor Jitco, Inc., 1776 East Jefferson Street, Rockville, Maryland 20852
(4) Now with Bureau of Veterinary Medicine, Food and Drug Administration, 5600 Fishers Lane, Rockville, Maryland 20857
(5) Bioassay Program, National Toxicology Program, Research Triangle Park, Box 12233, North Carolina 27709 and Bethesda, Maryland 20205
(6) Now with Clement Associates, 1010 Wisconsin Avenue, Washington, DC 20007 (7) Now at 4208 Dresden Street, Kensington, Maryland 20795 (8) EG&G Mason Research Institute, 1530 East Jefferson Street, Rockville,
Maryland 20852 (9) Mathematical Statistics and Applied Mathematics Section, Biometry
Branch, Field Studies and Statistics, Division of Cancer Cause and Prevention, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20205
(10) Midwest Research Institute, 425 Volker Boulevard, Kansas City, Missouri 64110
REVIEWERS
National Toxicology Program Board of Scientific Counselors' Technical Reports Review Subcommittee
Margaret Hitchcock, Ph.D (Chairperson) Pharmacology/Toxicology
John B. Pierce Foundation Laboratory New Haven, Connecticut
Curtis Harper, Ph.D. Alice Whittemore, Ph.D* (Principal Reviewer) (Principal Reviewer) Associate Professor of Biostatistics Pharmacology Stanford University School University of North Carolina of Medicine Chapel Hill, North Carolina Palo Alto, California
Subcommittee Panel of Experts
Norman Breslow, Ph.D* Biostatistics University of Washington Seattle, Washington
Joseph Highland, Ph.D. Toxicology Environmental Defense Fund Washington, D.C.
Frank Mirer, Ph.D. United Auto Workers International Union Detroit, Michigan
Sheldon Murphy, Ph.D. University of Texas Medical School Houston, Texas
Svend Nielsen, D.V.M., Ph.D. Professor of Pathology The University of Connecticut Storrs, Connecticut
Bernard Schwetz, Ph.D. (Principal Reviewer) Toxicology Research Laboratory Dow Chemical U.S.A
Midland, Michigan
Roy Shore, Ph.D. Statistics New York University Medical Center New York, New York
James Swenberg, Ph.D. Chief of Pathology Chemical Industry Institute of Toxicology Research Triangle Park, North Carolina
Gary Williams, M.D. Chief of Experimental Pathology American Health Foundation Valhalla, New York
*Unable to attend February 18, 1981, meeting
XI
SUMMARY OF PEER REVIEW COMMENTS
On February 18, 1981, this carcinogenesis bioassay report on guar gum was peer-reviewed and approved by the National Toxicology Program Board of Scientific Counselors' Technical Reports Review Subcommittee and associated Panel of Experts at an open meeting held in Building 31C, National Institutes of Health, Bethesda, Maryland.
Dr. Schwetz, a principal reviewer for the technical report on the carcinogenesis bioassay of guar gum, agreed with the conclusion that guar gum was not carcinogenic for F344 rats or B6C3F1 mice of either sex. He commented that there were two batches of test material with differing purity, one of 83.5 percent and the other of 91.9 percent, and it was not identified as to whether either was food grade. Further, the stability of guar gum in the feed was not characterized, nor were the concentrations verified. He said the summary should state that 50,000 ppm, the upper dose level, is the upper limit recommended for feeding studies in the bioassay program. He indicated that more information should be given in the introduction about the earlier study by Krantz, especially on the strain of rat used. The duration over which food consumption was measured should be stated. Finally, Dr. Schwetz was critical of the poorly controlled environmental conditions under which the animals were maintained. The temperature range of 17 to 31 degrees C and the humidity range of 10 to 88 percent were intolerable.
As Dr. Whittemore, another principal reviewer, was not present, Dr. Hitchcock read her review. Dr. Whittemore, in her review, also agreed with the conclusion of the report. She reported that pituitary adenomas were significantly elevated in dosed male rats as compared with controls, but not in female rats or in mice. Non-malignant adrenal pheochromocytomas were significantly elevated in female rats, but this difference could be due to better survival in dosed rats. She said that an MTD was probably not reached but realized that this was because 50,000 ppm was the upper limit for feeding studies under program guidelines. Dr. Harper, as a third principal reviewer, noted that there were increased incidences of fibromas of subcutaneous tissues in male rats (0/50, 1/50,4/50).
Dr. Schwetz moved that the report on the bioassay of guar gum be accepted and the summary be revised to state that 50,000 ppm is the upper limit recommended for chronic feeding studies. Dr. Harper seconded the motion and the report was approved unanimously by the Peer Review Panel.
Xlll
I. INTRODUCTION
Guar gum (CAS No. 9000-30-0) is the milled endosperm of the leguminous
plant Cyanopsis tetragonolobus. Structurally, it is a galactomannan
consisting of a main chain of D-mannose with a side chain of D-galactose at
approximately every second mannose unit. The mannose units are /3-(l-4)
linked, and the single D-galactose units are joined to the main chain by
d -(1-6) linkages. The molecular weight is 220,000 (Chudzikowski, 1971).
Guar gum is approved for use as a food additive by the U.S. Food and
Drug Administration and is on the list of substances "generally recognized
as safe" (CFR 1974). The Food Chemicals Codex (1972) specifies that guar
gum contain not less than 66.0% galactomannans and not more than 15% water,
10% protein, 7% acid-insoluble material, and 1.5% ash. It is widely used in
the food industry as a stabilizer for ice cream, as a thickener or stabilizer
for beverages, salad dressings, and pie fillings, and as a binder in pro
cessed meat (Furia, 1972). The following products may contain guar gum at
the approximate concentrations listed: breakfast cereals, processed vege
tables, sweet sauces, and cheeses (1,200-7,800 ppm); milk products and imita
tion dairy products (1,700-4,200 ppm); fruit ices, fats and oils, snack
foods, and frozen dairy products (1,200-2,700 ppm); beverages, baked goods,
processed fruits, and soups (1,200 ppm); condiments and relishes, meat pro
ducts, and gelatin puddings (200 ppm) (Life Sciences Research Office, 1973).
Guar is used in cosmetics as an emulsifier and stabilizer and in
Pharmaceuticals as a tablet binder and disintegrant, an appetite depressant,
a laxative, and a treatment for peptic ulcers (Kirk and Othmer, 1966; Merck,
1968).
Guar is used in industry as an additive to strengthen paper; a sizing
and finishing agent for textiles; a thickener for dyestuffs, battery
electrolytes, printing inks, agricultural sprays, and caulking materials; a
stabilizer for foams and flotation materials (in mining); and as a binder,
thickener, a stabilizing agent for enamels and porcelain (Kirk and Othmer,
1966).
In 1970, 13 million kilograms of guar gum were imported into the United
States (Life Sciences Research Office, 1973). More recent production figures
are not available.
The oral LD-^ of guar gum is 8.1 g/kg for mice and 9.4 g/kg for rats
(Bailey and Morgareidge, 1976).
When tested without metabolic activation, guar gum was mutagenic for
Saccharomyces cerevisiae D-3, but not for Salmonella typhimurium TA 1530 or
G-46 (Green, 1977). Guar gum caused chromosome aberrations in human embry
onic lung cells (WI-38) (Green, 1977).
No compound-related histopathologic effects were observed in the liver,
kidney, spleen, gut, or bone marrow when groups of 7 or 8 rats (strain
unknown) of either sex were fed diets containing 50,000 ppm guar gum for 24
months (Krantz, 1948).
Guar gum was tested by the Bioassay Program because of its widespread
use in food. The only previous test for carcinogenicity was considered
inadequate because only one species was used and because the number of
animals was considered small by current standards (Krantz, 1948).
II. MATERIALS AND METHODS
A. Chemical
Guar gum was obtained in two batches from Stein Hall Company (Louisville,
KY), a division of the Celanese Polymer Specialties Company. Lot No. A-40-F
was used for the Subchronic studies and the first 3 months of the chronic
studies. Lot F10-77-966-1 was used for the remainder of the chronic studies.
Purity and identity analyses were performed at Midwest Research Institute
(Appendix E). Results from the titration of hydrolysis products by periodate
oxidation indicated that Lot No. A-40-F was 83.5% pure and that Lot No. F10
77-966-1 was 91.9% pure relative to glucose. Results of Karl Fischer titra
tions indicated 7.3% water in Lot No. A-40-F and 4.9% water in Lot No.
F10-77-966-1. Mannose and galactose were identified by thin-layer chromato
graphy as the major and minor components, respectively, in the hydrolysates
of both batches. A trace impurity was detected in the hydrolysate of Lot
No. F10-77-966-1. The infrared spectra of both batches were consistent with
the literature spectra. The bulk compound was stored in the dark at 4 C.
Throughout the course of the studies, the bioassay laboratory monitored
the chemical by infrared spectroscopy and saw no change in the spectra.
B. Dietary Preparation
Test diets were prepared by first mixing the chemical with an aliquot of
Wayne Lab Blox^ meal (Table 1) in a mortar and pestle and then layering this
mixture in a Patterson-Kelly* twin-shell V-blender (without an intensifier
bar) with the remainder of the feed and mixing for 10 minutes. Test diets
were sealed in labelled plastic bags and stored at 4°C for no longer than
7 days.
Due to similar components in guar gum and the feed, the quantitative
method available could not measure chronic dose levels of guar gum in feed
Table 1. Source and Description of Materials Used for Animal Maintenance
Item
Animal Feed
Feed Hoppers
Cages
Filter Sheets
Bedding
Description
Wayne Lab Blox^Meal
Stainless steel, gang style
Polycarbonate
Disposable, nonwoven fiber
Hardwood chips:
Aspen bed
Beta® Chips
Source
Allied Mills (Chicago, IL)
Scientific Cages, Inc. (Bryan, TX)
Lab Products, Inc. (Rochelie Park, NJ)
Lab Products, Inc. (Rochelie Park, NJ)
American Excelsior (Baltimore, MD)
Agway Corp. (Syracuse, NY)
reproducibility within 1̂0%. Thus, formulated diets were not analyzed for
concentrations of guar gum during the study.
C. Animals
Subchronic
Three-week-old F344 rats and 4-week-old B6C3F1 mice were obtained from
the NCI Frederick Cancer Research (Frederick, Maryland). The animals were
observed for 7 days and then assigned to control or dosed groups in such a
manner that average cage weights were approximately equal.
Chronic
Four-week old F344 rats and 4- to 5-week-old B6C3F1 mice were obtained
from the NCI Frederick Cancer Research Center, Frederick, Maryland. The
animals were observed for 2 weeks, randomly assigned to individual cages,
and the cages were randomly assigned to dosed and control groups.
D. Animal Maintenance
Rats and mice were housed five per cage in suspended polycarbonate cages
equipped with disposable nonwoven filter sheets (Table 1). Hardwood chip
bedding and cages were changed twice weekly, and cage racks were changed
every 2 weeks. Water and Wayne Lab Blo'x̂ meal were available ad libitum,
the former supplied through an Edstrom automatic watering system and the
latter in stainless steel, gang-style hoppers that were changed once per
week.
The temperature of animal rooms was 17 -31 C (average 23 C) and
relative humidity was controlled (10%-88%). Incoming air was filtered
through Tri-Dek 15/40 denier Dacron filters, with 10 room air changes per
hour. Fluorescent lighting was provided 12 hours per day.
Rats and mice were housed by species in separate rooms in which chronic
feeding studies were being conducted on di(2-ethylhexyl)phthalate (CAS 117
81-7), butyl benzyl phthalate (CAS 85-68-7), and di(2-ethylhexyl)adipate
(CAS 103-23-1).
E. Acute Oral Toxicity and Repeated Dose Studies
Acute oral and repeated dose feed studies were conducted using F344 rats
and B6C3F1 mice to determine the toxicity of guar gum and the concentrations
to be used in the Subchronic studies.
In the acute study, five males and five females of each species were
administered a single dose (0.42 g/kg) of the test substance in water by
gavage. No mortality or compound-related effects were observed. All animals
were killed on day 15.
In the repeated dose study, groups of five males and five females of
each species were fed diets containing 0, 6,300, 12,500, 25,000, 50,000, or
100,000 ppm guar gum for 2 weeks. No mortality or compound-related effects
were observed. All animals were killed on day 15.
F. Subchronic Studies
Subchronic studies were conducted to determine the concentrations to be
used in the chronic studies. Diets containing 0, 6,300, 12,500, 25,000,
50,000, or 100,000 ppm guar gum were fed for 13 weeks to groups of 10 males
and 10 females of each species (Tables 2 and 3).
Mortality and morbidity checks were made twice daily; individual animals
were weighed and feed consumption by cage was determined weekly. At the end
of the 91-day study, survivors were killed, necropsies were performed on all
animals, and tissues (see section H) were taken for histopathologic
examinations.
Table 2. Dosage, Survival, and Mean Body Weights of Rats Fed Diets Containing Guar Gum for 91 Days
Dose Survival Mean Body Weights (grams) (ppm) (a) Initial Final Change
MALE 0 10/10 112 339 +227
6,300 10/10 110 332 +222
12,500 10/10 111 332 +221
25,000 10/10 112 327 +215
50,000 10/10 111 322 +211
100,000 10/10 111 302 +191
FEMALE 0 10/10 95 195 +100
6,300 10/10 97 202 +105
12,500 10/10 95 195 +100
25,000 10/10 94 198 +104
50,000 9/10 95 197 +102
100,000 9/10 95 192 +97
(a) Number surviving/number per group (b) Weight Change Relative to Controls =
Rats; Two female rats died; one receiving 50,000 ppm and one receiving
100,000 ppm. Weight gain as compared with controls was depressed 16% in
male rats receiving 100,000 ppm. A dose-related decrease in feed consumption
was observed for rats of either sex. Feed consumption by rats fed 100,000
ppm was 80% that of the controls. No compound related clinical signs or
histopathologic effects were detected.
Doses selected for rats for the chronic study were 25,000 ppm and 50,000
ppm, since the upper limit recommended for chronic feeding studies in the
Bioassay Program is 50,000 ppm (NCI, 1976).
Micet One female mouse receiving 100,000 ppm died. Weight gain as com
pared with controls was depressed by 15% or 16% in female mice receiving
50,000 or 100,000 ppm. Feed consumption by dosed mice of either sex was
comparable with or higher than that of the corresponding controls. No com
pound related clinical signs or histopathologic effects were observed.
Doses selected for mice for the chronic study were 25,000 or 50,000 ppm
guar gum in feed.
G. Chronic Studies
The number of animals per group, the concentrations of guar gum adminis
tered in the feed, and the duration of the chronic studies are shown in Table
4. Dosed groups were given diets containing guar gum for 103 consecutive
weeks, followed by 1 to 3 weeks on basal diet.
H. Clinical Examinations and Pathology
Animals were observed twice daily for morbidity and mortality; individual
clinical signs, individual body weights and feed consumption by cage were
recorded every 4 weeks. The mean animals in the group by the number of (sur
viving) animals in the group. The average feed consumption per animal was
calculated by dividing the total feed consumption measured for all cages by
the number of surviving animals in the group. Animals that were moribund
Table 4. Experimental Design of Chronic Feeding Studies with Guar Gum in Rats and Mice
Initial Test No. of Guar Gum Weeks on Study Group Animals (ppm) Dosed (a) Not Dosed
Male Rats
Untreated-Control (b) 50 0 0 105
Low-Dose 50 25,000 103 1
High -Dose 50 50,000 103 1
Female Rats
Untreated-Control (b) 50 0 0 104-105
Low-Dose 50 25,000 103 1
High -Dose 50 50,000 103 1
Male Mice
Untreated-Control (b) 50 0 0 106
Low-Dose 50 25,000 103 3
High -Dose 50 50,000 103 2
Female Mice
Untreated-Control (b) 50 0 0 106
Low-Dose 50 25,000 103 3
High -Dose 50 50,000 103 3
(a) The start dates were August 8, 1977 for rats and May 12, 1977 for mice. The kill dates were August 8, 1979 for rats and May 18, 1979 for mice.
(b) Control and dosed groups were of the same strain, sex, and age range and from the same source and shipment. All animals of the same strain shared the same room, and all aspects of animal care and maintenance were similar. Animals were randomized to dosed and control groups as described in Section II.C.
10
and those that survived to the end of the study were killed using carbon
dioxide inhalation and necropsied.
Gross and microscopic examinations were performed on major tissues,
organs, and all gross lesions from killed animals and from animals found
dead unless precluded in whole or in part by autolysis or cannibalization.
Thus, the number of animals from which particular organs or tissues were
examined microscopically varies and does not necessarily represent the number
of animals that were placed on study in each group.
The tissues were preserved in 10% neutral buffered formalin, embedded in
paraffin, sectioned, and stained with hematoxylin and eosin. The following
were examined microscopically: skin (abdominal), lungs and bronchi, trachea,
bone, bone marrow (femur) and thigh muscle, spleen, lymph nodes, thymus,
(a) Dosed groups received doses of 25,000 or 50,000 ppm in the diet. (b) Number of tumor-bearing animals/number of animals examined at site
(percent). (c) Beneath the incidence of tumors in the control group is the probability
level for the Cochran-Armitage test when P is less than 0.05; otherwise, not significant (N.S.) is indicated. Beneath the incidence of tumors in a dosed group is the probability level for the Fisher exact test for the comparison of that dosed group with the untreated control group when P is less than 0.05; otherwise, not significant (N.S.) is indicated.
(d) A negative trend (N) indicates a lower incidence in a dosed group than in a control group.
(e) The 95 percent confidence interval of the relative risk between each dosed group and the control group.
27
Table 7. Analyses of the Incidence of Primary Tumors in Female Rats Fed Diets Containing Guar Gum (a)
(a) Dosed groups received doses of 25,000 or 50,000 ppm in the diet. (b) Number of tumor-bearing animals/number of animals examined at site
(percent). (c) Beneath the incidence of tumors in the control group is the probability
level for the Cochran-Armitage test when P is less than 0.05; otherwise, not significant (N.S.) is indicated. Beneath the incidence of tumors in a dosed group is the probability level for the Fisher exact test for the comparison of that dosed group with the untreated control group when P is less than 0.05; otherwise, not significant (N.S.) is indicated.
(d) A negative trend (N) indicates a lower incidence in a dosed group than in a control group.
(e) The 95 percent confidence interval of the relative risk between each dosed group and the control group.
(f) The probability level for departure from linear trend is given when P is less than 0.05 for any comparison.
32
IV. RESULTS - MICE
A. Body Weights and Clinical Signs (Mice)
After 20 weeks the mean body weight of high-dose female mice was consis
tently lower than that of the corresponding controls (Figure 3 and Table 8).
No compound-related clinical signs were observed. A decrease in feed con
sumption was observed for mice of either sex (Appendix F). For male mice
feed consumption in the low- and high-dose groups averaged 82% and 84% of
the control values, respectively. For female mice the corresponding figures
were 88% and 92%.
B. Survial (Mice)
Estimates of the probabilities of survival of male and female mice fed
diets containing guar gum at the concentrations of this bioassay, together
with those of the control group, are shown by the Kaplan and Meier curves in
Figure 4. The survival of the untreated control group of male mice was
significantly lower than the survival of the high-dose group. No significant
differences in survival were observed between the two dosed groups. No
significant differences were observed between any of the groups of female
mice.
In male mice, 33/50 (66%) of the untreated controls, 41/50 (82%) of the
low-dose, and 43/50 (86%) of the high-dose group lived to the end of the
study at 105-106 weeks. In female mice, 38/50 (76%) of the untreated con
trols, 35/50 (70%) of the low-dose, and 36/50(72%) of the high-dose group
lived to the end of the study at 106 weeks.
C. Pathology (Mice)
Histopathologic findings on neoplasms in mice are summarized in Appendix
B, Tables Bl and B2; findings on nonneoplastic lesions are summarized in
(a) Dosed groups received doses of 25,000 or 50,000 ppm in the diet. (b) Number of tumor-bearing animals/number of animals examined at site
(percent). Only those animals living beyond 52 weeks are included in the denominators except for the occurrence of malignant lymphoma where all animals living 49 weeks and beyond are included, because of the observation of one animal in the high-dose group with such a tumor at 49 weeks.
(c) Beneath the incidence of tumors in the control group is the probability level for the Cochran-Armitage test when P is less than 0.05; otherwise, not significant (N.S.) is indicated. Beneath the incidence of tumors in a dosed group is the probability level for the Fisher exact test for the comparison of that dosed group with the untreated-control group when P is less than 0.05; otherwise, not significant (N.S.) is indicated.
(d) A negative trend (N) indicates a lower incidence in a dosed group than in a control group.
(e) The 95 percent confidence interval of the relative risk between each dosed group and the control group.
(f) The probability level for departure from linear trend is given when P is less than 0.05 for any comparison.
42
Table 10. Analyses of the Incidence of Primary Tumors in Female Mice Fed Diets Containing Guar Gum (a)
(a) Dosed groups received doses of 25,000 or 50,000 ppm in the diet. (b) Number of tumor-bearing animals/number of animals examined at site
(percent). (c) Beneath the incidence of tumors in the control group is the probability
level for the Cochran-Armitage test when P is less than 0.05; otherwise, not significant (N.S.) is indicated. Beneath the incidence of tumors in a dosed group is the probability level for the Fisher exact test for the comparison of that dosed group with the untreated-control group when P is less than 0.05; otherwise, not significant (N.S.) is indicated.
(d) A negative trend (N) indicates a lower incidence in a dosed group than in a control group.
(e) The 95 percent confidence interval of the relative risk between each dosed group and the control group.
(f) The probability level for departure from linear trend is given when P is less than 0.05 for any comparison.
46
V. DISCUSSION
After week 20 in mice and week 40 in rats, the mean body weights of high-
dose females were lower than those of the untreated cdntrols. No compound-
related clinical signs or adverse effects on survival were observed. Average
feed consumption was reduced in all dosed groups of rats and mice when
compared with the controls.
A variety of tumors was seen in control and dosed animals; none are
clearly associated with administration of guar gum. The incidence of
adenomas observed in the pituitary was significantly greater in the dosed
groups of male rats than in the controls but more male rats with carcinomas
were observed in the control group than in the dosed groups with the overall
result that there was no statistically significant difference in the
combined incidence of animals with these tumors. Similarly, pheochromo
cytomas of the adrenal of female rats were observed in the dosed groups at
incidences significantly higher than that in the controls, but there was no
significant increase in the combined incidence of female rats with
pheochromocytomas or malignant pheochromocytomas.
Hepatocellular carcinomas occurred in dosed male mice at incidences
significantly lower than those in the controls. The combined incidence of
male mice with either hepatocellular adenomas or carcinomas was also signifi
cantly lower in the high-dose group than in the controls.
In the only other available study, no compound-related histopathologic
effects were observed when 7-8 rats (strain unknown) of either sex were fed
Two other galactomannan, legume-derived gums (locust bean gum, NTP 1982a
and tara gum, NTP 1982b) were tested at the same laboratory as the present
study. Besides these, two additional "gums" have been tested recently by the
NTP bioassay program (agar, NTP 1982c and gum arabic, 1982d). Each of the
four gums was added to the diet (2.5% and 5%) and fed for 104 weeks to F344
rats and B6C3F1 mice of each sex. Under these test conditions all were
considered not carcinogenic.
48
VI. CONCLUSION
Under the conditions of this bioassay, guar gum was not carcinogenic for
F344 rats or B6C3F1 mice of either sex.
49
VII. BIBLIOGRAPHY
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52
Appendix A
Summary of the Incidence of Neoplasms in Rats Fed Diets Containing Guar Gum
53
TABLE A1.
SUMMARY OF THE INCIDENCE OF NEOPLASMS IN MALE RATS FED DIETS CONTAINING GUAR GUM
CONTROL LOW DOSE
ANIMALS INITIALLY IN STUDY 50 50 ANIMALS NECROPSIED 50 50 ANIMALS EXAMINED HISTOPATHOLOGICALLY 50 50
Modification of U. S. P. Assay for Mannitol (USP, 1970).
Samples were dissolved in 25 ml of concentrated sulfuric acid and 150 ml water in 250-ml volumetric flasks and left at room temperature for 65 hours. The solutions were then boiled for 55 minutes on a hot plate. The flasks were cooled and diluted to volume with water. Aliquouts (5 ml) were transferred to 125-ml Erlenmeyer flasks with 50.0 ml potassium periodate/sulfuric acid solution added. One sample and the blank were heated on a steam bath for 25 hours.