Progesterone effect mediated by the voltage-dependent calcium channel and protein kinase C on noncapacitated cryopreserved bovine spermatozoa

An increase in intracellular calcium is essential to trigger capacitation a nd the acrosome reaction. The aim of this study was to determine the proges terone effect mediated by the voltage-dependent calcium channel and protein kinase C on heparin-capacitated and non-capacitated spermatozoa. Protein k inase C was activated by 1-oleoyl-2-acetyl glycerol, a membrane-permeant di acyl-glycerol, and inhibited by GF-109203X. The percentage of true acrosome reaction was evaluated using differential-interferential optical contrast microscopy and trypan blue stain. The calcium concentration was evaluated b y FURA-2AM and methoxy-verapamil was used as a voltage-dependent calcium ch annel inhibitor. A rapid calcium increase and acrosome reaction were induce d by progesterone in capacitated and noncapacitated spermatozoa, a higher i ntracellular calcium increase being observed in capacitated than in noncapa citated samples (P<0.05). The calcium increase and acrosome reaction were b locked significantly by GF-109203X in noncapacitated and capacitated sperma tozoa by the addition of progesterone and/or 1-oleoyl-2-acetylglycerol. Met hoxyverapamil blocked calcium influx in samples treated with progesterone a nd heparin/progesterone, but not in those treated with 1-oleoyl-2-acetyl gl ycerol. Progesterone induces the acrosome reaction in noncapacitated cryopr eserved bovine spermatozoa through intracellular mechanisms dependent on pr otein kinase C and the voltage-dependent calcium channel.