Effect of gossypol‐acetic acid on calcium transport and ATPase activity in plasma membranes from ram and bull spermatozoa

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Abstract
The effects of gossypolacetic acid on the activity of Mg-ATPase and Ca-Mg-ATPase and on Ca uptake by plasma membranes from ram and bull spermatozoa were examined. The 2 parameters were almost completely inhibited by 10 .mu.M gossypol for both ram and bull sperm. To assess the effects of higher gosspol concentrations, isolated membrane vesicles were loaded with Ca by operating the ATP-dependent Ca pump, after which gossypol was added and Ca uptake followed. At 10 .mu.M gossypol, additional Ca uptake was 85% inhibited while at 40 .mu.M a release of the accumulated Ca was observed. The inhibitory effect of 10 .mu.M gossypol was almost completely reversible by simple dilution of gossypol-treated membranes; at 40 .mu.M the effect was only 50% reversible. The data show a high degree of similarity between bull and ram, suggesting minimal differences between the 2 spp as far as the structure and function of the sperm plasma membrane is concerned.