Effects of spironolactone (aldosterone antagonist) on electrolyte and water content of the cauda epididymidis and fertility of male rats.

It has previously been shown that the rat cauda epididymidis actively reabsorbs Na+ in exchange with K+. This coupled Na+/K+ transport is stimulated by aldosterone. These transport processes create a low Na+ and high K+ environment which appears to be (in part) responsible for sperm quiescence during storage. The effects of aldosterone antagonist, spironolactone, on the electrolyte and water content of the cauda epididymidis, sperm motility initiation and fertility of male rats were investigated in the present study. It was found that treatment of rats with spironolactone (10 mg/kg per day for 4 to 17 days) led to a significant fall in K+ (18%) and sperm (21.5%) concentrations in the cauda epididymal fluid. However, the Na+ concentration remained unchanged. The fall in sperm concentration may be taken to indicate an increase in fluid volume which is secondary to an inhibition of water absorption. When corrected for an increase in volume, there was no change in the amount of K+ in the fluid but the amount of intraluminal Na+ was increased. Despite a fall in K+ and sperm concentration, the capacity of the cauda sperm to initiate motility and fertility of the animals were apparently not affected by spironolactone treatment. It is concluded that the fertility capacity of spermatozoa is rather resistant to drugs which interfere with electrolyte and water transport across the caudal epididymal epithelium.