Potentiation of the cGMP-induced Guinea pig acrosome reaction by zinc

Abstract
The addition of 8 bromo cGMP (10 mM) immediately (∼2 min) upon suspension of Guinea pig sperm in glucose-free BWW medium induces a significant number of acrosome reactions within minutes. The simultaneous addition of micromolar concentrations of ZnCl2 (25–1000 μM) potentiates the cGMP effects. Mid-micromolar concentrations were able to dramatically increase the percentage of acrosome reactions by a factor of 6.5 over 8 bromo cGMP alone. The induction of acrosome reactions was dependent upon external Ca++, and it is suggested that in this species Zn++ flnctions by affecting cyclic nucleotide metabolism and/or Ca++ flux.