Calcium uptake and Ca2+-ATPase activity in goat spermatozoa membrane vesicles do not require Mg2+.

Microsomal membrane vesicles isolated from goat spermatozoa contain Ca2+- ATPase, and exhibit Ca2+ transport activities that do not require exogenous Mg2+ .The enzyme activity is inhibited by calcium-channel inhibitors, e.g. verapamil and diltiazem, like the well known Ca2+ , Mg2+-ATPase. The uptake of calcium is ATP (energy)- dependent and the accumulated Ca2+ can be completely released by the Ca2+ ionophore A23187, suggesting that a significant fraction of the vesicles are oriented inside out.