Effects of an Inhibitor of Adenylate Cyclase on Acrosome Reaction Induced by Protein Kinase C Activators

Abstract

To determine whether the adenylate cyclase and the protein kinase C pathways act independently to modulate the human sperm acrosome reaction, we studied the effects of 2′-O-methyladenosine (adenylate cyclase inhibitor) on acrosome reactions induced by protein kinase C activators (phorbol diesters and synthetic diacylglycerols) or an adenylate cyclase stimulator (forskolin: FR). Fifty aliquots of capacitated spermatozoa were divided into 5 groups (A, B, C, D, and E), each containing 10 samples. One control aliquot (CN) and five experimental aliquots (EX1, EX2, EX3, EX4, and EX5) were prepared from each sample. Phorbol 12-myristate, 13-acetate (PMA, 10 μmol/L), 4β-phorbol 12,13-didecanoate (PDD, 0.1 μmol/L), l-oleoyl-2-acetyl-.wi-glycerol (OAG, 50 μmol/L), 1,2-dioctanoyl-sn-glycerol (DOG, 50 μmol/L), or FR (10 μrnol/L) was added to each of the experimental aliquots in groups A, B, C, D, and E, respectively. Increasing concentrations of 2′-O-methyladenosine were added to aliquots EX2, EX3, EX4, and EX5. After an incubation period of 25 min at 37°C, it was found that the percentage of acrosome-reacted spermatozoa (%ARS) was significantly and dose-dependently decreased by 2′-O-methyladenosine concentrations of 1 mM or more. Within each group, the %ARS was significantly higher in EX1 aliquots than in CN aliquots. The reduction of acrosome reactions induced by protein kinase C activators by the adenylate cyclase inhibitor suggests that the protein kinase C pathway interacts with the adenylate cyclase pathway to modulate the human sperm acrosome reaction.

Key Words:

• Sperm
• Acrosome reaction
• Adenylate cyclase
• Protein kinase C.