N-bis(2-hydroxypropyl)nitrosamine誘発ラット甲状腺腫瘍における性ホルモンの影響

Abstract

The effect of sex hormone on the development of thyroid tumors in rats treated with N-bis(2-hydroxypropyl)nitrosamine (DHPN) was studied. In experiment 1, the incidences of thyroid adenomas induced by DHPN (210 mg/100 g body weight×2) at the end of the experiment for 30 weeks were 35% in non-castrated rats, 100% in non-castrated rats treated with 500 ppm phenobarbifal diet, 20% in castrated rats, 55% in castrated rats treated with 300 ppm testosterone (T) diet and 36% in castrated rats treated with 0.75 ppm estradiol diet. In experiment 2, the incidences of thyroid carcinomas induced by DHPN (210 mg/100 g body weight×4) at the end of the experiment for 30 weeks were 68% in non-castrated rats, 52% in castrated rats, 55% in castrated rats treated with 100 ppm T diet, 66% in castrated rats treated with 300 ppm T diet, 72% in castrated rats treated with 600 ppm T diet, and 40% in castrated rats treated with 900 ppm T diet. Castration decreased the incidence of thyroid tumors in rats treated with DHPN. T (300 ppm～600 ppm) increased and T (900 ppm) decreased the incidence of thyroid tumors in castrated rats treated with DHPN, but estrogen did not. Serum TSH levels did not show the dose response of T in rats treated with DHPN and castration.