The effect of theophylline and dibutyryl cyclic AMP on the uptake of radioactive calcium and phosphate ions by boar and human spermatozoa

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Abstract
Radioactive Ca uptake by suspensions of washed boar and human spermatozoa was inhibited by the mitochondrial uncoupling agent carbonylcyanide-p-trifluoromethoxy-phenylhydrazone (FCCP). Theophylline + dibutyryl cyclic(c)AMP also inhibited Ca uptake in the presence or absence of FCCP. Uptake of low concentrations of Ca (0.1 mM) was inhibited by the Ca ionophore A23187, but at high Ca concentrations the ionophore stimulated Ca uptake. These observations are explained by a mechanism for Ca uptake regulation in spermatozoa based on competing mitochondrial and plasma membrane pumps. Uptake of 32P was also inhibited. Apparently, cAMP is involved in the transport of ions across the plasma membrane of spermatozoa.