INVOLVEMENT OF ADRENERGIC SYSTEM ON THE CORTICAL GRANULE EXOCYTOSIS AND POLYSPERMIC PENETRATION DURING IN-VITRO FERTILIZATION OF PORCINE OOCYTES

The effects of propranolol, a beta-adrenergic blocker, and epinephrine on cortical granule exocytosis and polyspermic penetration in the pig were determined. Pig oocytes precultured in medium containing 1 and 1 0 mu M propranolol had an increased (P < 0.05) percentage of polysperm ic penetration. The mean number of spermatozoa penetrating oocytes pre cultured in 1 and 10 mu M propranolol was also higher (P < 0.01) than that in the control group. Cortical granule exocytosis in oocytes afte r sperm penetration was observed by either transmission electron or ep ifluorescence microscopy. Preculture of oocytes in media containing 1 and 10 mu M propranolol significantly (P < 0.05) decreased the inciden ce of cortical granule exocytosis and increased abnormal patterns of c ortical granule exocytosis. Preculture of pig oocytes with 1 and 10 mu M epinephrine did not increase monospermic penetration and complete c ortical granule exocytosis. However, combined pretreatment of oocytes with 10 mu M propranolol and 10 mu M epinephrine decreased polyspermic penetration and incomplete cortical granule exocytosis compared with that of oocytes precultured with 10 mu M propranolol alone. These resu lts suggest that the intracellular adrenergic system is involved in co rtical granule reaction in the pig and that defects of the adrenergic system may be related to a high incidence of polyspermy in the pig. (C ) 1997 by Elsevier Science Inc.