MAMMALIAN TESTIS 



339 



active spermatogenesis in the androgen- 

 treated, hypophysectomized rat. Comparing 

 such steroids as testosterone, androsterone, 

 dehydroisoandrosterone, androstenedione, 

 and various isomers of androstenediol, they 

 concluded that the ability of androgens to 

 maintain spermatogenesis is not related to 

 their androgenicity. In fact, the weaker the 

 androgen the better is the maintenance of 

 spermatogenesis after hypophysectomy. 

 This observation is important for it shows 

 that maintenance of spermatogenesis is not 

 due to the induction by androgen of a favor- 

 able scrotal environment for the testis. In 

 further studies, Nelson (1941) showed that 

 spermatogenesis could be maintained for 



^? f.'^ 





178 days after hypophysectomy by testos- 

 terone propionate. No difference was ob- 

 served between spermatogenesis under these 

 conditions and that which occurs normally. 

 Motile sperm were formed, and the animals 

 could copulate with and impregnate females. 

 The only difference was that the testes in 

 the hypophysectomized animals treated 

 with testosterone were only one-sixth nor- 

 mal size. 



As is true of other effects of androgens on 

 the testis, the time at which rats are hy- 

 pophysectomized seems to be a critical fac- 

 tor in the ability of testosterone to maintain 

 spermatogenesis. Leathern (1942, 1944) 

 showed tliat troatmcnt witli tostosterone in 



Fig. 5.19A. Effect of testosterone on the testis of the rat. 4, normal rat, 30 days of age. 

 S, normal rat, 60 days of age. 6, 30-day-old rat given 10 ^g- of testosterone propionate daily 

 for 30 days (no inhibition of spermatogenesis). 7, 30-day-old rat given 100 ^ig. of testosterone 

 propionate daily for 30 days (suppression of spermatogenesis). 



