26 The Biochemistry of Semen 



Prostaglandin y vesigiandin, and certain other pharmacodynamically 

 active substances 



Among the more striking pharmacological effects of seminal 

 plasma are a depressor action on blood vessels, and a stimulation 

 of isolated smooth-muscle organs such as the uterus and the intes- 

 tines. Both these effects which have been studied in great detail by 

 von Euler (1934«, b\ 1935, 1937, 1939, 1949) and Goldblatt (1933, 

 1935^?) are due in all probability not to a single substance but to the 

 combined action of several constituents of seminal plasma, including 

 choline and two substances which Euler has named 'prostaglandin* 

 and 'vesigiandin'. So far, only prostaglandin has been purified. 

 The purest preparation obtained from ram prostate glands has been 

 found by Bergstrom (1949) to be nitrogen-free, and to contain an 

 unsaturated acidic substance which absorbs strongly ultraviolet light 

 with a maximum at 280 m//. When assayed on the isolated intestine 

 of rabbit, 1/^g. of this substance exhibited the same activity as the 

 crude extract from 500 mg. prostatic tissue. Assuming that the sub- 

 stance is pure, the total content of prostaglandin in 100 kg. prostate 

 glands must be of the order of 25-50 mg. To prepare this quantity, 

 one would require the glands from 20,000 rams. 



The physiological significance of prostaglandin and vesigiandin in 

 reproduction processes is unknown but it has been suggested that 

 they represent some sort of 'automatic regulator' which controls 

 the voiding of the secretions from the prostate and the seminal 

 vesicle, respectively. The idea of chemical stimulation by secretory 

 products is based among others, on observations that the emptying 

 of the prostate and seminal vesicle leads to a decreased ability of 

 these glands to contract which persists until enough of freshly 

 formed secretion has accumulated. 



A pharmacodynamic influence of the seminal plasma upon some 

 parts of the female reproductive tract has also been envisaged but 

 the evidence is derived mainly from experiments on isolated organs. 

 It remains questionable whether any of the effects exerted by the 

 seminal plasma on the uterus and oviduct in vitro, also occur in the 

 female reproductive tract in vivo (Barnes, 1939; Asplund, 1947). 



Kurzrok and Lieb (1931) found on adding 1 ml. of human seminal 

 fluid to a strip of human uterus suspended in a 100 ml. bath, either 



