P-31 NMR studies of phosphate metabolism in the ovulatory process induced by gonadotropins in perfused rabbit ovary

The concentrations of phosphate metabolites were measured in perfused rabbi t ovaries before, during and after ischemia, and during the ovulatory proce ss induced by the administration of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCC) using P-31 NMR spectroscopy. A decr ease in adenosine triphosphate (ATP) and an increase in inorganic phosphate (Pi) during ischemia were observed. After reperfusion of the ovary, both A TP and Pi levels returned to their initial control levels. These results ar e in agreement with the results observed in other organ tissues. On the oth er hand, ATP levels rapidly decreased dose dependently with infusion of HCG during 10 h of perfusion. A decrease in ovarian ATP concentration after in fusion of HCG was also confirmed by enzymatic analysis of the extracts from ovarian tissues. On the other hand, significant changes in Pi levels were not observed throughout the perfusion period. Furthermore, significant chan ges in phosphomonoester (PME) levels, adenosine diphosphate (ADP) levels an d intracellular pH were not observed before and during the infusion of HCG. The concentration of cyclic adenosine 3',5'-monophosphate (cAMP) in the pe rfusate after the perfusion was also measured during the ovulatory period. Within 30 min cAMP significantly increased dose dependently and reached pea k levels within 60 min. The concentration of cAMP then gradually decreased. Ovulatory efficacy during the infusion of HCG was also observed. These res ults suggest that the decreased ATP in the successive processes leading to ovulation probably reflects protein phosphorylation through the activation of the cAMP-dependent protein kinases prior to induction of various chemica l reactions related to the initiation of ovulation. Copyright (C) 1999 John Wiley & Sons, Ltd.