The effects of sodium and amiloride on the motility of the caudal epididymal spermatozoa of the rat

Summary The forward motility of the rat caudal epididymal spermatozoa has been studied in different Na⁺ concentrations. When spermatozoa were suspended in a completely Na⁺-free solution, the forward motility suffered a progressive fall and after 3 h was completely suppressed. This effect was fully reversible on resuspending the spermatozoa in a solution containing Na⁺. Amiloride caused a fall in motility and the effect was similar to that of Na⁺ removal. The inhibition by amiloride of the motility was concentration dependent and the dose response curve showed an IC₅₀-value of about 5×10^–5 M. The role of Na⁺ influx in the maintenance of sperm motility was discussed.This work was supported by the World Health Organization.The technical assistance of Mr C.M. Li and the gift of amiloride from Merck, Sharp and Dohme are gratefully acknowledged.