340 



PHYSIOLOGY OF GONADS 



rats Itypophysectomized at 27 days of age 

 resulted in the production of spermatids, 

 but spermatogenesis did not occur. How- 

 ever, if the animals were operated on at 33 

 days of age, testosterone induced the forma- 

 tion of sperm. Furthermore, if the atrophic 

 testes of hypophysectomized rats were stim- 

 ulated by a gonadotrophin (PMS), testos- 

 terone also maintained the spermatogenesis 

 thus induced. 



It is not known exactly how testosterone 

 maintains spermatogenesis after hypophy- 

 sectomy. It seems that the "maintenance 

 type" of spermatogenesis is not the same as 

 spermatogenesis resulting from gonado- 

 trophin, because the seminiferous tubules 

 of the androgenically maintained testes in 

 hypophysectomized rats are small. The ef- 



fect of androgen is not produced simply by 

 the maintenance of sperm cells already pres- 

 ent in the testis at the time of hypophysec- 

 tomy because Nelson (1941) showed that 

 spermatogenesis can be reinstituted in the 

 testis of a hypophysectomized rat in spite of 

 delaying treatment with testosterone for 3 

 to 4 weeks after hypophysectomy. This in- 

 terval of time exceeds the normal sojourn of 

 sperm cells in the epididymis; thus the 

 results in terms of siring young cannot be 

 attributed to sperm cells already present in 

 the accessory duct system at the time of 

 hyjjophysectomy (Figs. 5.19, A and B, and 

 5.20). 



The dose of testosterone propionate nec- 

 essary for maintenance of spermatogenesis 

 in the rat seems to be around 80 fig. per day. 



9^-: v;: - n II 



Fig. 5.19B. 8, 3U-day-old mt given 1000 /ug. of testosterone propionate daily for 30 days 

 (no suppression of spermatogenesis). .9, 30-day -old rat given 8.4 mg. of estradiol daily for 30 

 days (])ronoun(ed inhibition of spermatogenesis). 10, 30-day-old rat given 8.4 ng. of estradiol 

 and 1000 mS- of lestosterone i)ro])ic)nale for 30 days (no inhir)ition of spermatogenesis). 

 (From D. J. Jjudwig, Endocrinology, 46, 453, 1950.) 



