Abstract
Uterine quiescence and activity during pregnancy are regulated by local generation and action of prostaglandins. In this study, we measured the activity of phospholipase A2, that is responsible for release of their precursor arachidonic acid, in the rat uterus and cervix throughout gestation and at parturition. Phospholipase A2 activities of both uterine and cervical cytosol were relatively low until day 15 of pregnancy, showed highest values from days 21 to 23 (the delivering day) of pregnancy, and declined by day 2 postpartum. Prostaglandin F2a levels in both tissues showed similar fluctuations with greater amplitudes to those of phospholipase A2 activity during gestation. The enhanced enzyme activity on the day of delivery was mostly suppressed by the specific inhibitor for cytosolic phospholipase A2. Immunohistochemical examination revealed cytosolic phospholipase A2 localization in uterine endometrial epithelial cells, longitudial myometrium, and cervical connective tissue. Obtained data show the presence of cytosolic phospholipase A2 in rat uterine myometrium and cervix and its activity was regulated during pregnancy. They also suggest that the enhanced activity of this enzyme may contribute to muscle contraction and cervical dilatation at parturition through local prostaglandin synthesis.
