Virilizing effect of methyltestosterone on female descendants in the rat.

Pregnant rats were given daily a subcutaneous injection of methyltestosterone for 4 days from the 17th to the 20th day of gestation, and were allowed to be delivered to their offsprings (F1) which were used for the examination of later reproductive functioning. When observed for 21 weeks after birth, the growth rate of F1 from methyltestosterone-treated groups was higher than that of F1 from the control group. The anogenital distance in 50-microgram-treated F1 females started to become significantly longer on the 14th day and in 5-microgram-treated F1 females on the 28th day after birth than that in F1 from the control. The day on which vaginal opening took place in 50% of females was 34.4 days of age in both the control and the 5 microgram groups, but it delayed until 40.7 days in the 50 microgram group. Furthermore, persistent estrus was observed after about 90 days of age in the 50 microgram group. This persistent estrus disappeared by placing these females with males, resulting no pregnancy. In the 5 microgram group females could be pregnant, but their female fetuses (F2), when examined on the 21st day of gestation, had significantly shortened the length of the urovaginal septum. The observations show that virilization can be induced in the third generation.