146 The Biochemistry of Semen 



after the operation contains no more than 20 ^g. fructose, as com- 

 pared with 500 to 1000 /^g., before the operation. Both castrated as 

 well as hypophysectomized animals promptly respond to the sub- 

 cutaneous implantation or injection of testosterone with renewed 

 secretion of fructose. The same happens if instead of testosterone 

 pregnant mare serum gonadotrophin is injected into a hypophy- 

 sectomized animal (Table 21). 



The relationship between blood glucose and seminal fructose 



In addition to the hormones of the testis and the pituitary gland, 

 yet another organ, the pancreas, exerts a profound influence upon 

 the level of fructose in semen. The effect is an indirect one, and is 

 brought about by the action of insulin on the level of blood glucose 

 which in turn governs the level of fructose in semen. The existence 

 of a causal link between the blood sugar level and seminal fructose 

 was studied at first in animals with experimental diabetes; later, 

 however, it was also shown in diabetic man (Mann and Parsons, 

 1949, 1950). 



In rabbits, experimental diabetes can be produced with alloxan; 

 best results are obtained by injecting intravenously into a rabbit 

 75 mg. alloxan per kg. body weight, and repeating this dose one or 

 two days later. Fig. 14 illustrates the course of such an experiment 

 with a rabbit in which analyses of blood and semen were carried 

 out regularly during a period of four months. At the outset of the 

 experiment this animal had a blood glucose content of 100 mg. per 

 100 ml., and about 600 i-ig. fructose per ejaculate or 70 mg. per 

 100 ml. semen (fluid portion). However, following alloxan treatment, 

 the rabbit developed severe glucosuria within two days and its blood 

 glucose level rose to 350 mg./lOO ml.; at the same time, the level of 

 fructose in semen began to increase, until three weeks later there 

 was 500 mg. glucose per 100 ml. blood, and 3500 /^g. fructose per 

 ejaculate or 320 mg. fructose per 100 ml. semen. When it was estab- 

 lished that hyperglycaemia is followed by an increased concentra- 

 tion of fructose in semen, the effect of insulin was examined and it 

 was found that the insuUn-induced fall in blood glucose was followed 

 by a reduction in the fructose content of semen; moreover, once the 

 effect of insulin on blood glucose in the diabetic animal wore off, 

 there was again an increase in seminal fructose. 



