Fructose and Fructolysis 149 



diet (Marrian and Parkes, 1928; Dunn, Morris and Dubnik, 1947; 

 Elson and Koller, 1948). 



Lutwak-Mann and Mann (1950a, b, 1951) applied chemical 

 methods to the study of changes brought about in the secretory 

 function of rat accesory organs by vitamin B-deficiency and inani- 

 tion, and found that in rats maintained for four weeks on a deficient 

 diet the content of fructose and citric acid in the accessory glands 

 was reduced to a castrate level. By treatment with testosterone pro- 

 pionate (0-2 mg. daily for one week) or with chorionic gonadotro- 

 phin (200 units every other day for two weeks), the secretory activity 

 of the glands could be completely restored. A further example of the 

 effect of an unbalanced diet on the process of fructose secretion was 

 provided by Lutwak-Mann (1951) who found that a diet with exces- 

 sive fat content, even though not protein- or vitamin-deficient, also 

 caused regression in rat accessory organs. Mann and Walton (1953) 

 made a study of the effect of underfeeding on the genital functions 

 in the bull and found that, in contrast to the testes, the secretory 

 function of the male accessory glands was markedly affected by 

 underfeeding. The concentration of fructose and citric acid in the 

 semen of the underfed bull decreased by 30% and 60% respectively, 

 of the original levels. In the bull, however, unlike in the rat, the 

 effects of malnutrition as well as the recovery after the animal has 

 been transferred back to its normal diet, developed comparatively 

 slowly. 



The enzymic mechanism of fructose formation 



The experimental evidence available at present brought out the 

 essential, though as yet not fully understood, role of the testicular 

 hormone in the formation of fructose by the secretory apparatus 

 of the male accessory glands, and indicated that blood glucose is 

 the precursor of seminal fructose. Further details of the mechanism 

 whereby glucose is converted in the accessory gland tissue to fruc- 

 tose, were obtained from in vitro experiments; these showed that 

 small amounts of fructose are formed as a result of incubation of 

 minced accessory gland tissues with glucose, and that these tissues 

 possess the entire enzymic system which can convert glucose to 

 fructose (Mann and Lutwak-Mann, 1948, \95\a, b). 



It is an estabUshed fact that certain phosphorylated derivatives of 



