Calcium and phospholipase A2 are both required for the acrosome reaction mediated by G-proteins stimulation in human spermatozoa

• Published in: Molecular reproduction and development 1999-03, Vol.52 (3), p.297-302
• Main Authors: Domínguez, L., Yunes, R.M.F., Fornés, M.W., Burgos, M., Mayorga, L.S.
• Format: Article
• Language: English
• Subjects: acrosome reaction; Acrosome Reaction - drug effects; Acrosome Reaction - physiology; arachidonic acid; Arachidonic Acid - metabolism; Biological and medical sciences; Calcimycin - metabolism; Calcimycin - pharmacology; calcium; Calcium - metabolism; divalent cation chelators; Fundamental and applied biological sciences. Psychology; GTP-binding proteins; GTP-Binding Proteins - metabolism; Guanosine 5'-O-(3-Thiotriphosphate) - metabolism; Hormone metabolism and regulation; human spermatozoa; Humans; Ionophores - metabolism; Ionophores - pharmacology; Male; Mammalian male genital system; Phospholipases A - metabolism; Phospholipases A2; Spermatozoa - drug effects; Spermatozoa - physiology; Vertebrates: reproduction
• ISSN: 1040-452X; 1098-2795
• DOI: 10.1002/(SICI)1098-2795(199903)52:3<297::AID-MRD7>3.0.CO;2-T

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 (GTPγS, 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 GTPγS 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. Mol. Reprod. Dev. 52:297–302, 1999. © 1999 Wiley‐Liss, Inc.