Abstract
To investigate the presence and possible physiological role of cytosolic phospholipase A2 (cPLA2) in corpora lutea (CL), immunoblot analysis and activity measurements of the enzyme were performed on the cytosol of rat CL. The mouse monoclonal antibody against human cPLA2 immunoprecipitated a single protein (ca 110 kDa Mr) in several rat tissues, and the immunoreaction decreased in the absence of EGTA during homogenization. These results suggest that the antibody can recognize rat cPLA2. Subsequent immunoblot analysis detected little cPLA2 in adult rat CL on days 6 and 12 of pregnancy. In both adult and immature rats, the enzyme protein was not detectable in CL on day 6 of pseudopregnancy (PSP6); however, it became detectable in CL of PSP12. In these models, luteal cytosolic PLA2 activity, as determined by the release of fatty acid from liposomes of phosphatidylcholine, clearly increased from PSP6 to PSP12, and the increase persisted during treatment with the secreted PLA2 inactivator ditiothreitol. The present results suggest a possible involvement of cPLA2 in luteal eicosanoids production and luteolytic processes.
