Differential distribution of cyclic-AMP receptors in human spermatozoa

The binding properties of cyclic-AMP to intact and fractionated in heads and tails human spermatozoa have been studied. Whole spermatozoa bound 6.8 +/- 0.8 pmol of cyclic-AMP per 10(7) cells. Binding of cyclic-AMP was selectively located in the midpiece-tail region of the spermatozoa. Thus only 18% of the binding in the whole sperm could be accounted for by the binding on the sperm heads. This distribution is similar to that previously described for the protein kinase of bovine sperm. Blocking membrane sulfhydryl groups with pCMBS induced a drastic inhibition (65%) of the cyclic-AMP binding to the sperm heads, while only moderately reducing (30%) the binding in the sperm tails