NATIONAL TOXICOLOGY PROGRAM Technical Report Series No. 291 c TOXICOLOGY AND CARCINOGENESIS STUDIES OF ISOPHORONE (CAS NO. 78-59-1) IN F344/N RATS AND B6C3F1 MICE (GAVAGE STUDIES) U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service National Institutes of Health NATIONAL TOXICOLOGY PROGRAM The National Toxicology Program (NTP), established in 1978, develops and evaluates scientific information about potentially toxic and hazardous chemicals. This knowledge can be used for protecting the health of the American people and for the primary prevention of disease. By bringing together the relevant programs, staff, and resources from the U.S.Public Health Service, DHHS, the National Toxicology Program has centralized and strengthened activities relating to toxicology research, testing and test developmentlvalidation efforts, and the dissemination of toxicological information to the public and scientific communities and to the research and regulatory agencies. The NTP is made up of four charter DHHS agencies: the National Cancer Institute (NCI), Naiional Institutes of Health; the National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health; the National Center for Toxicological Research (NCTR), Food and Drug Administration; and the National Institute for Occupational Safety and Health (NIOSH), Centers for Disease Control. In July 1981, the Carcino- genesis Bioassay Testing Program, NCI, was transferred to the NIEHS. Isophorone, NTP TR 291 NTP TECHNICAL REPORT ON THE TOXICOLOGY AND CARCINOGENESIS STUDIES OF ISOPHORONE (CAS NO. 78-59-1) IN F344/N RATS AND B6C3F1 MICE (GAVAGE STUDIES) NATIONAL TOXICOLOGY PROGRAM P.O. Box 12233 Research Triangle Park, NC 27709 January 1986 NTP TR 291 NIH Publication No. 86-2547 U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service National Institutes of Health NOTE TO THE READER These studies are desi ned and conducted to characterize and evaluate the toxicologic potential, in- cluding carcino enic acfivit ,of selected chemicals in laboratory animals (usuall two species, rats and mice). Chemica4 s selected Jrtestin in the NTP Carcinogenesis Pro ram are c osen primarily on the bases of human exposure, level of ro%uction,and chemical structure. Eelection perx se is not an indicator ?fa chemical’s carcinogenic poten1 !al. 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 has the potential for 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. Five categories of interpretative conclusions were adopted for use in June 1983in the Technical Reports series to specifically emphasize consistency and the concept of actual evidence of carcinogenicity. For each definitive study result (male rats, female rats, male mice, female mice), one of the following-quintet will be selected to describe the findings. These categories refer to the strength of the experimental evidence and not to either potency or mechanism. 0 Clear Evidence of Carcinogenicity is demonstrated by studies that are interpreted as showing a chemically related increased incidence, of malignant neo lasms, studies that exhibit a substantially increased incidence of beni neoplasms, or sfudies that exhibit an increased incidence of a combination of malignant anEenign neoplasms where each increases with dose. 0 Some Evidence of Carcino enicjt is demonstrated by studies that are inter reted as showing a chemically related increase5 inci&nce of. benign neoplasms, studies thaf exhibit margmal increases in neoplasms of several organs/tissues, or studies that exhibit a slight increase in uncommon malignant or benign neoplasms. 0 Equivocal Evidence of Carcinogenicity is demonstrated by studies that are interpreted as showing a chemically related marginal increase of neoplasms. 0 No Eyidence of Carcinogenicity is demonstrated by studies that are interpreted as showing no chemically related increases in malignant or benign neoplasms. 0 Inadequate Stud of Carcinogenicity demonstrates that because of majpr qualitative or quantitative limita.r ions, the studies cannot be interpreted as valid for showing either the presence or absence of a carcinogenic effect. Additionally, the followin concepts (as atterned from the International A ency for Research on Cancer Monographs) have been acfopted by the JTPto give further clarification of tfese issues: This stud was initiated b the National Cancer Institute’s Carcinogenesis Bioassay Program now part of the NaEonal Institute of Environmental Health Sciences, National Toxicolo Program. The studies described in this Technical Report have been conducted in com liance with 86 P chemical health and safet requirements and must meet or exceed all applicable FeAral, state, and local health and safety regu?ations. All NTP toxicology and carcinogenesis studies are subjected to a data audit before being presented for peer review. Althou h every effort is made to prepare the Technical Re orts as accurately as possible, mistakes may occur. Weaders are re uested to identify any mistakes so tRat corrective action.may be taken. Further anyone who is aware o4 related ongoing or ublished studies not mentioned in this re rt 1s encouraged td make this information known to the NT f:. Comments and uestions about the ational Toxicolo Program Technical Reports on Toxicolo and Carcino enesis &dies should be directed to Dr. J.E. H8 National Toxicology Program, P.O. Boxy2233, Researca Triangle Park, NC 27709 (919-541-3780). These NTP Technical Reports are available for sale from the National Technical Information Service, U.S.De artment of Commerce, 5285 Port Royal. Road, Springfield, VA 22161 !703-487-4650).Sin le copies OF this Technical Re or! are available without char e (and while supplies last) from the N9 P Public Information Office, 8ational Toxicology Program, P.6. Box 12233,Research Triangle Park, NC 27709. Isophorone, NTP TR 291 2 CONTENTS PAGE ABSTRACT .............................................................................. 10 CONTRIBUTORS ......................................................................... 12 PEER REVIEW PANEL ................................................................... 13 SUMMARY OF PEER REVIEW COMMENTS ................................................. 14 I. INTRODUCTION ................................................................... 15 II. MATERIALS AND METHODS ........................................................ 21 PROCUREMENT AND CHARACTERIZATION OF ISOPHORONE ........................ 22 PREPARATION OF DOSE MIXTURES .............................................. 23 SIXTEEN-DAY STUDIES .......................................................... 24 THIRTEEN-WEEK STUDIES ....................................................... 24 TWO-YEAR STUDIES ............................................................. 24 STUDY DESIGN ............................................................... 24 SOURCE AND SPECIF'ICATIONS OF ANIMALS .................................... 24 ANIMAL MAINTENANCE ....................................................... 27 CLINICAL EXAMINATIONS AND PATHOLOGY .................................... 27 STATISTICAL METHODS ....................................................... 27 III. RESULTS ......................................................................... 29 RATS .......................................................................... 30 SIXTEEN-DAY STUDIES ........................................................ 30 THIRTEEN-WEEK STUDIES ..................................................... 31 TWO-YEAR STUDIES .......................................................... 32 BODY WEIGHTS AND CLINICAL SIGNS ........................................ 32 SURVIVAL ................................................................. 34 PATHOLOGY AND STATISTICAL ANALYSES OF RESULTS ....................... 34 MICE ............................................................................. 39 SIXTEEN-DAY STUDIES ........................................................ 39 THIRTEEN-WEEK STUDIES ..................................................... 40 TWO-YEAR STUDIES .......................................................... 41 BODY WEIGHTS AND CLINICAL SIGNS ........................................ 41 SURVIVAL ................................................................. 43 PATHOLOGY AND STATISTICAL ANALYSES OF RESULTS ....................... 43 IV. DISCUSSION AND CONCLUSIONS .................................................... 49 V. REFERENCES ..................................................................... 55 3 Isophorone.NTP TR 291 TABLES PAGE TABLE 1 PROPERTIES OF ISOPHORONE ............................................... .I8 TABLE 2 IDENTITY AND SOURCE OF LOTS USED IN THE GAVAGE STUDIES OF ISOPHORONE ............................................................... 22 TABLE 3 PREPARATION AND STORAGE OF DOSE MIXTURES IN THE GAVAGE STUDIES OF ISOPHORONE ........................................................... .23 TABLE 4 SUMMARY OF RESULTS OF ANALYSIS OF DOSE MIXTURES IN THE TWO-YEAR GAVAGE STUDIES OF ISOPHORONE ..........................................