Calcium and phospholipase A2 are both required for the acrosome reaction mediated by G-proteins stimulation in human spermatozoa.
G-proteins, calcium, and phospholipase A2 (PLA2) have all been implicated in the cascade of signaling events leading to the acrosome reaction in human spermatozoa. In order to study the role of Ca+2 and PLA2 during the acrosome reaction triggered by G-proteins, we treated human spermatozoa incubated for 3 hr under capacitating conditions with several reagents (GTPgammaS, A23187, ONO-RS-082, arachidonic acid, BAPTA-AM, and TPEN), alone or in different combinations. Our results suggest that GTP-binding proteins require Ca+2 and PLA2 to accomplish their stimulatory effect, and that Ca+2 is also required when the acrosome reaction--bypassing the action of PLA2--is stimulated by AA. Accordingly, when treated with GTPgammaS or AA, the cells loaded with Fura 2-AM showed a steady increase of [Ca+2]i. On the other hand, a massive influx of Ca+2 was completely unable to induce the acrosome reaction if PLA2 was inhibited, suggesting that both an increase of [Ca+2]i and PLA2 activation are required for the acrosome reaction to occur.
Domínguez
L
L
Universidad Nacional de Cuyo, CONICET, Mendoza, Argentina.
Yunes
R M
RM
Fornés
M W
MW
Burgos
M
M
Mayorga
L S
LS
D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D016718:Arachidonic Acid / Q000378:metabolism; D000001:Calcimycin / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D007476:Ionophores / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*
D007476:Ionophores; D016718:Arachidonic Acid; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000001:Calcimycin; D010741:Phospholipases A; D054467:Phospholipases A2; D019204:GTP-Binding Proteins; D002118:Calcium