ACROSOMAL EXOCYTOSIS IN THE HUMAN SPERM, PARTICIPATION OF A PHOSPHOLIPASE A2 ACTIVATED BY A G-PROTEIN

DOMINGUEZ LA.; YUNES R.; FORNES MW.; BURGOS MH.; MAYORGA LS.

San Luis

Congreso; 7mo Congreso Argentino de Ciencias Morfológicas; 1996

Universidad del Salvador

ACROSOMAL EXOCYTOSIS IN THE HUMAN SPERM, PARTICIPATION OF A PHOSPHOLIPASE A2 ACTIVATED BY A G-PROTEINThe acrosome reaction (AR) is an exocytosis of the acrosome content which allows spermatozoa to fertilize the ovum. The molecular mechanism of AR is not well known. Many factors have been involved (G-proteins, phospholipases A2, C, D. Phospholipids, etc.). In previous studies we have observed that G-proteins activators produced the AR in the human sperm. In this study our aim was to obtain evidences of the participation of phospholipase A2 (PLA2) in AR and if the previous activation of a G-protein is required. Washed normal human sperm samples were exposed to the following treatments: 1) G-protein activator (GTPgS. 40uM); 2) PLA2 inhibitors: a non-specific one, dexamethasone (Dex. 1mM) and a specific one, 2-(p-amylcinnamoyl) amino-4-chlorobenzoic acid (ONO-RS-082, 320 ug/ml); and 3) PLA2 action derivatives, arachidonic acid (AA 50uM) and lysophosphatydilcholine (LPC 20 uM). Acrosome reaction was evaluated by light and fluorescence microscopy and transmission electron microscopy. Results as percentages of live reacted sperm showed that GTPgS, AA and LPC produced 69, 61 and 67%, respectively of increase in relation to control group (17%). The steroid Dex was able to block (23%) the stimulatory effect of GTPgS on AR which was reverted by AA y LPC (60 and 63%, respectively). On other hand, ONO-RS-082 also blocked (27%) the effect of GTPgS and this blocking was reverted by AA. These data allow us to suggest the role of a PLA2, activated by a G-protein, in the human sperm acrosomal exocytosis.