Abstract

The present study examined whether regulation of progesterone-enhanced hyperactivation of spermatozoa is associated with the production of inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) by phospholipase C (PLC) and cyclic adenosine monophosphate (cAMP) by adenylate cyclase (AC), as well as activation of protein kinase C (PKC) and protein kinase A (PKA). Hamster spermatozoa were hyperactivated by incubation for 4 h in modified Tyrode's albumin lactate pyruvate (mTALP) medium. In order to examine the effects of IP3 receptor (IP3R), PKC and PKA on progesterone-enhanced hyperactivation, their inhibitors (xestospongin C, bisindolylmaleimide 1 and H-89) were used. Progesterone-enhanced hyperactivation was significantly suppressed by the inhibitors of IP3R, PKC and PKA. The results suggest that progesterone-enhanced sperm hyperactivation occurs through two signal pathways. One is an intracellular Ca2+ signal through production of IP3 and DAG by PLC, binding of IP3 to IP3R and activation of PKC by DAG and Ca2+. The other is a cAMP-PKA signal through production of cAMP by AC and activation of PKA by cAMP.

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