Effect of intraluminal ion concentrations on the secretion of the rat cauda epididymidis in vivo.

It has been shown that the rat epididymis secretes proteins and organic compounds which may play a role in sperm maturation and storage. A method has been described to study caudal epididymal secretion in anaesthetized rats in vivo. The cauda epididymidis was luminally perfused with Krebs bicarbonate solution. The perfusate collected at the vas deferens was allowed to flow through a microcell and absorption at 280 nm was monitored and displayed on a recorder. Secretion as measured by this method was found to be independent of perfusion rate ranging from 2.8 to 25 microliter/min and was maintained over a period of 8 h. Removal of Na+ ions from the perfusion fluid had no effect on the secretion rate. Removal of Ca2+ by perfusion of the duct with a Ca2+-free EGTA (1.5 mM) solution caused a rise in the secretion rate as revealed by an increase in absorption of the perfusate. High potassium produced similar results. Analysis of the perfusates showed that the Ca2+-free EGTA solution caused an increase in the secretion of non-protein materials whilst high potassium stimulated the release of proteins. Luminal application (0.5 mg/ml) or intraperitoneal injection (30 or 80 mg/kg) of cycloheximide had no effect on secretion during the 6 h post-treatment period. These results are discussed in relation to the possible mechanism of secretion in the epididymis.