Effects of ouabain on spermatozoan function: a review.

The cardiac glycoside, ouabain, exerts its influence on spermatozoa by binding to and inhibiting Mg2+-activated Na+, K+-dependent ATPase that is located in the midpiece-tail membranes. Ouabain decreased intracellular potassium, increased intracellular sodium, and produced a biphasic and time-dependent effect on motility--stimulation at low concentrations and inhibition at high concentrations. The motility depression consisted of decreases in numbers of motile cells, percent progressive motility, beat frequency, and amplitude. Species differences and maturational age of the sperm cells were reflected in the degree of the ouabain effect and also the distribution of the ouabain-sensitive enzyme. The presence of this enzyme in spermatozoan membranes contributes significantly to regulation of sperm cell function through modulation of cationic fluxes which in "conventional" cell types influence their excitability.