MAMMALIAN TESTIS 



335 



soluble hormone (testosterone) responsible 

 for maintaining the accessories. The ob- 

 servations of Vidgoff and his associates were 

 disputed by Rubin (1941). The inhibin con- 

 cept was supported by McCullagh and 

 Hruby (1949) because testosterone did not 

 inhibit the excretion of pituitary gonado- 

 trophin and was not effective in correcting 

 castration changes in the pituitary of crypt- 

 orchid rats at doses that were sufficient 

 to stimulate the accessories. Inhibin was 

 now identified with estrogen, and the source 

 of estrogen was claimed to be the Sertoli 

 cell. The new evidence for this modified con- 

 cept will now be considered. 



]\IcCullagh and Schaffenburg (1952) 

 stated that estrogen is much more effective 

 than androgen in suppressing gonado- 

 trophin and that estrogen is present in saline 

 extracts of bull and human sperm. Estrogen 

 is found in the testes, but localization of its 

 production to the Sertoli cells is uncertain 

 (Teilum, 1956), and is doubted by Morii 

 (1956) and Ballerio (1954). The almost 

 complete absence of Sertoli cells in Kline- 

 felter's syndrome, in which values for uri- 

 nary gonadotrophin are high, also is 

 considered as evidence that estrogen is man- 

 ufactured by the Sertoli cells. The high ex- 

 cretion of gonadotrophin in Klinefelter's 

 syndrome can be interpreted, at least in 

 part, by the concept of Heller, Paulsen, 

 ^lortimore, Jungck and Nelson (1952) that 

 the amount of urinary gonadotrophin varies 

 inversely with the state of the germinal epi- 

 thelium. Utilization of gonadotrophins by 

 the germinal epithelium could explain the 

 levels of this hormone in various syndromes 

 as satisfactorily as the lack of a hypothetic 

 testicular inhibitory hormone. Furthermore, 

 if the Sertoli cells secrete an inhibitory 

 hormone, patients who have germinal 

 aplasia (Sertoli cells only in the tubules) 

 should have normal values for urinary 

 gonadotrophin, whereas it is well known 

 that this hormone is greatly increased in 

 these patients. The proponents of the in- 

 hibin theory claim that aqueous extracts of 

 testes prevent the castration changes but do 

 not repair the accessories, whereas testos- 

 terone corrects the accessories but does not 

 restore the normal histologic appearance of 

 the pituitary. However, Nelson showed that 

 cryptorchid testes produce less androgen 



than normal and that the order in which the 

 above structures are affected represents dif- 

 ferences in the degree of their sensitivity 

 to the amount of androgen produced. The 

 efficacy of aqueous extracts on the cytologic 

 appearance of the pituitary has not been 

 confirmed. Thus, evidence deduced from 

 cryptorchism that an inhibitory hormone is 

 produced by the germinal epithelium is 

 inadequate. 



XII. Effects of the Pituitary on the 

 Testis 



Little information has been added in the 

 past 20 years to the effects of acute hypo- 

 physeal deprivation on the mammalian 

 testis. Smith (1938, 1939) had shown in the 

 rat that spermatocytes as well as sperma- 

 togonia and Sertoli cells remain for a long 

 time after hypophysectomy. However, in 

 the monkey, and possibly in man, all cells 

 of the germinal line except the spermato- 

 gonia and the Sertoli cells disappear. Even 

 though hypophysectomy has been employed 

 for several years as a palliative procedure 

 in inoperable carcinoma of the prostate, no 

 data have been obtained concerning the 

 effects of hypophysectomy on the testis 

 in otherwise normal man. In the dog, the 

 testes decrease to about one-third their 

 normal weight after surgical removal of the 

 pituitary. Only a single row of spermato- 

 gonia remains (Fig. 5.18). The Leydig cells 

 are reduced in size and contain abundant 

 quantities of fat. The lack of complete in- 

 volution of the Leydig cells in the dog as 

 a result of hypophysectomy is somewhat 

 unusual, because marked involution of these 

 cells occurs in all other mammals thus far 

 studied. With respect to the behavior of the 

 germinal epithelium, the dog (Huggins and 

 Russell, 1946) seems to be more like the 

 monkey and man than like the rat and 

 mouse. The total relative decrease in testic- 

 ular weight of the dog is intermediate be- 

 tween that observed in the cat (50 per cent) 

 and that in the rat, guinea pig, and rabbit 

 (75 per cent). With respect to histologic 

 features, the guinea pig and ferret are in- 

 termediate between the rat and the monkey, 

 because occasional spermatocytes remain in 

 addition to spermatogonia and Sertoli cells. 

 In the mouse, the testicular weight decreases 

 for 25 days after hypophysectomy. Mess 



