Sustained activity of luteal cytosolic phospholipase A2 during luteolysis in pseudopregnant rats: its possible implication in tissue involution.

We investigated the expression and activity of cytosolic phospholipase A2 (cPLA2) in the corpus luteum during spontaneous and induced luteolysis in pseudopregnant rats. In both models, luteal PLA2 activity rose in association with functional regression and persisted during the following structural regression. Tissue concentration of prostaglandin F2alpha with a luteolytic potency showed a similar fluctuation. The enzyme activity was almost completely suppressed by a cPLA2-specific inhibitor. Expression of cPLA2, analyzed by immunohistochemistry, became enhanced during luteolysis with preferential localization to phagocytotic and fibrotic replacement sites. Taken together with our previous finding, the data indicate a persistent elevation in luteal cPLA2 expression and activity that may affect tissue involution in vivo.