ACCESSORY MAMMALIAN REPRODUCTIVE GLANDS 



381 



tracardiac injection, Zn*'^ is concentrated by 

 this tissue 15 to 25 times more than any 

 other organ, including the ventral prostate 

 (Gunn, Gould, Ginori and Morse, 1955). 

 The dorsolateral prostate of the rat consists 

 of two parts which are functionally and an- 

 atomically distinct, and only the lateral 

 portion concentrates Zn*'^ (Gunn and Gould, 

 1956a, 1957a). A rapid uptake of Zn^'s by 

 slices of the rat dorsolateral prostate in 

 vitro has been noted by Taylor (1957) . 



The zinc content of the rat dorsolateral 

 prostate, and its uptake of Zn*'^, are under 

 hormonal control. The concentration of zinc 

 in this gland increases 6- to 10-fold between 

 the 35th and 100th day of life (Fischer, Tik- 

 kala and IMawson, 1955). In the adult rat, 

 Gunn and Gould (1956b) observed a 

 marked decrease in Zn^^ uptake after cas- 

 tration, which could be prevented by an- 

 drogen treatment. In immature (Alihar, 

 Elcoate and JNIawson, 1957) and hypophy- 

 sectomized (Gunn and Gould, 1957b) ani- 

 mals, the administration of testosterone or 

 gonadotrophin increased the zinc levels and 

 the rate of Zn*'^ uptake, whereas estradiol 

 was ineffective. 



The physiologic function of the zinc in 

 seminal plasma is problematical. This metal 

 is an integral component of the enzyme 

 carbonic anhydrase. The distribution of 

 carbonic anhydrase among the various lobes 

 of the prostate gland was studied by Maw- 

 son and Fischer (1952). In the rat, the pos- 

 terior prostate contains about the same 

 amount of carbonic anhydrase as the eryth- 

 rocytes, whereas the ventral prostate con- 

 tains very little of this enzyme. The lateral 

 portion of the posterior prostate contains 

 about 6 times as much zinc as the median 

 part. But only a small portion of the zinc 

 in the rat dorsolateral prostate, and in hu- 

 man semen, can be accounted for as car- 

 bonic anhydrase (Mawson and Fischer, 

 1953). According to Gunn and Gould 

 (1958), dorsolateral prostatectomy, which 

 removes most of the zinc from semen, is 

 without influence upon either fecundity or 

 fertility in the rat. 



Fructose. The presence of a reducing and 

 yeast-fermentable sugar in mammalian se- 

 men has been known for some time (Mc- 

 Carthy, Stepita, Johnston and Killian, 1928; 



Huggins and Johnson, 1933). It was as- 

 sumed by early workers that this sugar was 

 glucose. Although Yamada (1933) reported 

 that human semen contained a sugar which 

 reacted as a ketose, it was not until 1945 

 that the nature of the main reducing sugar 

 in most mammalian semens was elucidated 

 by Thaddeus Mann. Using a highly specific 

 enzymatic method of estimation, Mann 

 (1946) showed that the semen of men and 

 many other mammals contains little or no 

 glucose. The reducing and yeast-fermentable 

 sugar of bull seminal plasma was isolated in 

 the pure state and identified as d( — ) -fruc- 

 tose on the basis of its optical rotation and 

 formation of methylphenyl fructosazone. 



Mann (1949) found fructose in the semen 

 of the bull, ram, boar, goat, opposum, rab- 

 bit, guinea pig, mouse, hamster, and man. 

 It is also present in the European mole 

 iTalpa) and hedgehog {Erinaceus) (Mann, 

 1956). Table 6.2 shows that the fructose 

 content of semen varies greatly from one 

 species to another. In the five species indi- 

 cated, the total fructose accounts for all 

 the yeast-fermentable carbohydrate pres- 

 ent, but these species also contain non- 

 fermentable sugars. The semen of some ani- 

 mals contains glucose. This is true of the 

 rabbit, in which both glucose and fructose 

 are detectable (]\lann and Parsons, 1950), 

 and the cock (Mann, 1954a), the semen of 

 which is devoid of fructose. Ketoses other 

 than fructose are found in certain semens. 

 For example, the vesicular and ampullar 

 secretions of the stallion possess carbohy- 

 drates which react in colorimetric tests as 



TABLE 6.2 

 Reducing sugars of semen 

 Values obtained from Mann (1946) and ex- 

 pressed in terms of milligrams of fructose per 100 

 ml. of semen. 



" Small amounts of glucose were occasionallj' 

 fovmd in rabbit semen by Mann and Par.-ons 

 (1950). 



