APPENDIX A CASE STUDIES OF COMPOUNDS CONTENTS List of Tables and Figures ...................................................A-3 COMPOUND 1: A THIONAMIDE THAT AFFECTS THE SYNTHESIS OF ACTIVE THYROID HORMONE; THYROID PEROXIDASE AND 5'-MONO- DEIODINASE INHIBITION .................................. A-5 EXECUTIVE SUMMARY ................................................. A-5 DETAILED DATA ........................................................A-6 1. Cancer Findings .....................................................A-6 2. Mechanistic Considerations .............................................A-7 a. Mutagenicity ......................................................A-7 b. Thyroid Growth ...................................................A-8 c. Hormones .......................................................A-10 d. Site of Action ....................................................A-11 e. Dose Correlations .................................................A-12 f. Ancillary Data .................................................. A- 15 g. Structure-Activity Relationships ......................................A-17 h. Metabolic and Pharmacokinetic Properties ..............................A-17 3. Human Observations .................................................A-17 HAZARD AND DOSE-RESPONSE CHARACTERIZATION ......................A-18 BIBLIOGRAPHY ........................................................A-21 COMPOUND 2: A CHLORINATED CYCLIC HYDROCARBON THAT MAY INFLUENCE THE THYROID THROUGH EFFECTS ON THE LIVER; SIGNIFICANT DATA GAPS .................................A-24 EXECUTIVE SUMMARY .................................................A-24 DETAILED DATA .......................................................A-24 1. Cancer Findings ....................................................A-25 2. Mechanistic Considerations ............................................A-25 a. Mutagenicity .....................................................A-25 b. Thyroid Growth ..................................................A-25 c. Hormones .......................................................A-26 d. Site of Action ....................................................A-26 e. Dose Correlations .................................................A-27 f. Metabolism ......................................................A-27 g. Structure-Activity Relationships ......................................A-27 3. Human Observations .................................................A-28 HAZARD AND DOSE-RESPONSE CHARACTERIZATION ......................A-28 BIBLIOGRAPHY ........................................................A-30 A-1 CONTENTS (continued) COMPOUND 3: A BIS-BENZENAMINE THAT PRODUCES THYROID AND LIVER TUMORS; ANTITHYROID AND MUTAGENIC EFFECTS .........A-31 EXECUTIVE SUMMARY .................................................A-31 DETAILED DATA .......................................................A-31 1. Cancer Findings ....................................................A-31 2. Mechanistic Considerations ............................................A-33 a. Mutagenicity .....................................................A-33 b. Thyroid Growth .................................................A-33 c. Hormone Levels ..................................................A-33 d. Site of Action ....................................................A-34 e. Dose Correlations .................................................A-34 f. Metabolic and Pharmacokinetic Properties ..............................A-36 g. Structure-Activity Relationships ......................................A-36 3. Human Observations .................................................A-36 HAZARD AND DOSE-RESPONSE CHARACTERIZATION ......................A-36 BIBLIOGRAPHY ........................................................A-38 COMPOUND 4: A NITROSAMINE THAT IS MUTAGENIC AND HAS NO ANTITHYROID EFFECTS ................................................A-39 EXECUTIVE SUMMARY .................................................A-39 DETAILED DATA .......................................................A-39 1. Cancer Findings ....................................................A-40 2. Mechanistic Considerations ............................................A-40 a. Mutagenicity .....................................................A-41 b. Thyroid Growth .................................................A-41 c. Hormone Levels ..................................................A-43 d. Site of Action ....................................................A-44 e. Ancillary Data ..................................................A-44 f. Structure-Activity Relationships ......................................A-44 g. Metabolism and Pharmacokinetic Properties .............................A-44 3. Human Data .......................................................A-45 HAZARD AND DOSE-RESPONSE CHARACTERIZATION ......................A-45 BIBLIOGRAPHY ........................................................A-45 A-2 LIST OF TABLES A-1. F344 rats with thyroid follicular cell tumors in a 2-year study of compound 1 ..................................................A-6 A-2. B6C3F1 mice with thyroid follicular cell tumors in a 2-year study of compound 1 ..................................................A-7 A-3. Mean thyroid weights (mg) in male F344 rats after treatment with compound 1 for 28 days ...........................................A-8 A-4. Mean thyroid weights (mg) in F344 rats treated with compound 1 and sacrificed at 12 months ............................................A-9 A-5. Incidence of thyroid follicular cell hyperplasia in rats at 12 months ................A-9 A-6. Mean thyroid weights (gm) in rhesus monkeys after treatment with compound 1 for 13 weeks .........................................A-10 A-7. Serum T3, T4, and TSH levels in male F344 rats after treatment with compound 1 for 28 days ..........................................A-11 A-8. Effect of compound 1 on hepatic 5'- monodeiodinase in rats ...................A-12 A-9. Effect of T3 and T4 treatment on thyroid weights and serum T4, T3, and TSH levels in male rats given compound 1 over a 28-day period ..........A-16 A-10. Numbers (percent) of male rats with thyroid tumors at 20 weeks after treatment with DHPN followed by compound 1 .........................A-16 A-11. Numbers (percent) of rats with thyroid tumors (adenomas/carcinomas combined) .......................................A-25 A-12. Mean thyroid weights (mg) in male Sprague-Dawley rats treated for 90 days with compound 2 ..........................................A-26 A-13. T3 and T4 levels in male Sprague-Dawley rats treated with compound 2 for 14 days ..............................................A-26 A-14. Hepatic microsomal enzyme activities in male Sprague-Dawley rats treated for 14 days with compound 2 .................................A-27 A-15. Summary of effects relevant to evaluating the significance of thyroid tumors in rats ..............................................A-28 A-16. Rodents with liver and thyroid tumors in 2-year bioassays of compound 3 .....................................................A-32 A-17. Rats and mice with diffuse thyroid hyperplasia after 2 years of exposure to compound 3 ............................................A-34 A-18. Serum T4, T3, and TSH levels in male Wistar rats exposed to 400 ppm of compound 3 in water for 20 weeks ...........................A-35 A-19. Thyroid effects noted in the toxicity studies in rats and mice on compound 3 .....................................................A-35 A-20. Wistar rats with tumors by site in a 26-week study of compound 4 .......................................................A-40 A-3 LIST OF TABLES (continued) A-21. Thyroid follicular cell tumor incidence at 30 weeks in male and female Wistar rats treated with compound 4 by i.p. injection .........................A-41 A-22. Mean thyroid weights (mg) at 30 weeks in male and female Wistar rats treated with compound 4 by i.p. injection ........................A-42 A-23. Incidence of focal hyperplasia involving thyroid follicular cells at 30 weeks in male and female Wistar rats treated i.p. with compound 4 .............A-42 A-24. Serum T4 and TSH levels at 30 weeks in male and female Wistar rats treated i.p. with compound 4 .................................A-43 A-25. Comparison of serum TSH levels in rats with and without thyroid tumors induced by i.p. treatment with a cumulative dose of 600 mg/kg of compound 4 ..........................................A-43 A-26. Male rats with thyroid tumors at 20 weeks after a single treatment with compound 4 followed by PTU .....................................A-44 LIST OF FIGURES A-1. Thyroid Weight and Tumor Responses to Compound 1 ......................A-13 A-2. Hormone Responses to Compound 1 ................................... A-14 A-4 APPENDIX A: CASE STUDIES OF COMPOUNDS COMPOUND 1: A THIONAMIDE THAT AFFECTS THE SYNTHESIS OF ACTIVE THYROID HORMONE; THYROID PEROXIDASE AND 5'-MONO- DEIODINASE INHIBITION EXECUTIVE SUMMARY Compound 1 may pose a human thyroid carcinogenic hazard at high exposures that might be expected to produce disruptions in the thyroid-pituitary feedback loop. Given the extensive mode-of-action information showing that the thyroid follicular cell tumors are produced by stimulation of the thyroid by thyroid-stimulating hormone (TSH) and not due to mutagenic action, default nonlinear considerations will be employed to estimate concerns for human exposure. Compound 1 causes thyroid tumors in two rodent species and pituitary