Cyclooxygenase-2 and prostaglandin E-2(PGE(2)) receptor messenger RNAs areaffected by bovine oocyte maturation time and cumulus-oocyte complex quality, and PGE(2) induces moderate expansion of the bovine cumulus in vitro

Expression of cyclooxygenase-2 (COX-2) and prostaglandin E, (PGE,) receptor 2 (EP2) are necessary for rodent cumulus expansion in vivo. Prostaglandin E, receptor 3 (EP3) has been detected in bovine preovulatory follicles and corpora lutea. The current experiments examined the effect of PGE(2), on bo vine cumulus expansion in vitro and expression of COX-2, EP1, EP2, EP3, and EP4 mRNAs in bovine cumulus-oocyte complexes (COCs) at 0, 6, 12, 18, and 2 4 h time points during maturation in vitro. Concentrations of PGE(2), above 50 ng/ml resulted in moderate cumulus expansion of bovine COCs, but expans ion did not occur in the absence of serum. COX-2 mRNA expression increased in bovine COCs at 6 h and 12 h of maturation, then decreased. EP2 mRNA was detectable by reverse transcription-polymerase chain reaction at all time p oints. EP3 mRNA expression increased in COCs from 0 to 6 h and remained at this higher level through the culture period. Very low levels of EP4 mRNA e xpression were detectable, but EP1 was not detected in bovine COCs. Because EP receptor mRNAs and COX-2 mRNA are expressed in bovine COCs, there exist s the potential for a prostaglandin autocrine/paracrine regulatory pathway during oocyte maturation. Differential expression of the EP3 mRNA among var ying COC classes indicates that this gene product may be a useful marker of oocyte competence. Although the PGE(2), pathway is involved in cumulus exp ansion, serum factors are required to mediate PGE(2)-induced expansion.