ACCESSORY MAMMALIAN REPRODUCTIVE GLANDS 



393 



tective function in boar and stallion semen 

 seems an eminently reasonable one. How- 

 ever, the accessory glands of many animals 

 secrete certain substances {e.g., glycero- 

 phosphorylcholine, spermine, citric acid) 

 that do not appear to be of any particular 

 value for the survival of spermatozoa in 

 the male or female genital tracts. Perhaps 

 these substances are simply by-products 

 of the secretory mechanisms of the glands 

 from which they originate, or represent bio- 

 chemical vestiges. 



The widespread occurrence of fructose in 

 accessory gland secretions deserves further 

 comment. The only other situation where 

 large amounts of fructose are present in 

 mammalian extracellular fluids under nor- 

 mal physiologic conditions is in the fetal 

 blood of ungulates (Bernard, 1855; Bacon 

 and Bell, 1948; Alexander, Huggett, Nixon 

 and Widdas, 1955). Mammalian spermato- 

 zoa metabolize glucose just as well as fruc- 

 tose as a source of energy under anaerobic 

 and aerobic conditions. Indeed, glucose has 

 been used widely as the sole glycolyzable 

 sugar in artifi^l diluents employed in the 

 storage of semen for artificial insemination 

 (Mann, 1954a). Thus fructose does not 

 seem to be more beneficial than glucose 

 to the well being of spermatozoa. There is 

 evidence that the utilization of fructose, in 

 contrast to glucose, is not impaired in the 

 diabetic state (Chernick, Chaikoff and 

 Abraham, 1951 ; Renold, Hastings and Nes- 

 bett, 1954) . It is conceivable that the pres- 

 ence of fructose in semen w^ould render the 

 spermatozoa relatively insensitive to insu- 

 lin. But it would seem more probable that 

 the physiologic value of seminal fructose 

 is related to factors other than the matura- 

 tion or survival of spermatozoa. Mann 

 (1954a) has pointed out that if glucose 

 were the only glycolyzable sugar in semen, 

 its concentration would not be expected to 

 exceed that of blood. The transformation of 

 blood glucose into seminal fructose by the 

 accessory glands permits the establishment 

 of very high levels of fructose in semen. 

 Furthermore, the formation of seminal fruc- 

 tose is strictly controlled by androgenic 

 hormones, and it would be hard to conceive 

 of a similar hormonal dependence of glu- 

 cose levels in semen. 



Although the volume and chemical com- 



})osition of seminal plasma are influenced 

 by many factors, androgenic hormones are 

 undoubtedly the principal determinants of 

 the secretory activity of the accessory 

 glands. Chemical and enzymatic constit- 

 uents of accessory gland secretions such 

 as fructose, citric acid, and acid phospha- 

 tase have proved to be exquisitely sensitive 

 indicators of androgenic activity. The ap- 

 plication of such "chemical tests" for an- 

 drogen action has provided important 

 corroborative evidence for previous con- 

 clusions, based on purely morphologic 

 studies, that the initiation of mature secre- 

 tory function of the accessory glands pre- 

 cedes the appearance of sperm in the semi- 

 niferous tubules, and also that the adverse 

 effects of malnutrition on the functional 

 activity of the prostate gland and seminal 

 vesicle are mediated via the hypophysis. 

 Chemical investigations have established 

 that the major portion of certain compo- 

 nents (glycerojihosphorylcholine, glycosid- 

 ases ) of the seminal plasma of some species 

 originates from the epididymis. The way 

 to the successful treatment of metastatic 

 carcinoma of the prostate in man by anti- 

 androgenic measures was paved by the 

 availability of a chemical systemic index 

 of the hormonal dependence of many of 

 these neoplasias, viz., the acid phosphatase 

 of blood serum. Changes in the chemistry 

 of some accessory organs (e.g., the fructose 

 content of the rat coagulating glandj seem 

 to l)e more sensitive indicators of the ac- 

 tion of exogenous androgens in castrated 

 animals than the weights or histologic 

 structure of these organs. The application of 

 such chemical methods to the bioassay of an- 

 drogens holds much promise for the future. 

 Finally, it may be mentioned that chemi- 

 cal studies of the secretions of the accessory 

 glands have given insight into the homology 

 of these organs. The finding of high con- 

 centrations of citric acid, but not of fruc- 

 tose, in the rat female prostate after stim- 

 ulation with androgens shows that the 

 secretion of this tissue resembles that of the 

 ventral prostate gland of the male rat. On 

 the other hand, structures which are usu- 

 ally considered to be anatomically and 

 functionally homologous may secrete quite 

 different substances. Thus in the guinea 

 pig and bull, both citric acid and fructose 



