DIFFERENCES IN THE ROLE OF CYCLIC ADENOSINE-3',5'-MONOPHOSPHATE DURING CAPACITATION OF BOVINE SPERM BY HEPARIN OR OVIDUCT FLUID

Capacitation is an important maturational event in the life of a sperm atozoan that allows the sperm to undergo a stimulus-induced acrosome r eaction. Bovine sperm can be induced to undergo capacitation in vitro by heparin or oviduct fluid, and capacitation can be inhibited by gluc ose. We found that glucose did not interfere with H-3-heparin binding to sperm. Glucose inhibition of capacitation could be reversed in a do se-dependent manner by 8-bromo-cAMP or by the phosphodiesterase inhibi tors isobutylmethylxanthine or caffeine, with ED(50)s of 25, 32, and 1 83 mu M, respectively. The maximal effect of 8-bromo-cAMP on capacitat ion was during the first 2 h of a 4-h incubation. Sperm cAMP increased during capacitation with heparin from an initial value of 4.1 +/- 0.1 to 7.3 +/- 1.1 pmol cAMP/20 x 10(6) sperm at 4 h of incubation. Contr ol sperm cAMP at 4 h increased only to 4.9 +/- 0.8 pmol cAMP/20 x 10(6 ) sperm. There were both similarities and differences in the character istics of capacitation by heparin or oviduct fluid. Both glucose and p rotamine sulfate were found to suppress the heparin-dependent cAMP inc rease and inhibit capacitation. Capacitation by oviduct fluid was inhi bited by either glucose or protamine sulfate. A small increase in sper m cAMP was associated with capacitation by oviduct fluid but was not a ffected by glucose or protamine sulfate.