ACTIVATION OF PHOSPHOLIPASE-D BY PROSTAGLANDIN-F2-ALPHA IN RAT LUTEALCELLS AND EFFECTS OF INHIBITORS OF ARACHIDONIC-ACID METABOLISM

In rat luteal cells labeled with [H-3]oleic acid, PGF(2 alpha)-stimula ted phospholipase D (PLD) activation was investigated. The PLD activit y was detected by measuring the accumulation of [H-3]phosphatidylethan ol (PtdEt) in the presence of ethanol. PGF(2 alpha) stimulated PtdEt a ccumulation at concentrations of more than 100 nM in the presence of e thanol. However, PtdEt accumulation did not change in the absence of e thanol. PGF(2 alpha) (1 mu M) increased PtdEt accumulation after 1 min , and the accumulation reached a plateau by 2-3 min. These results ind icate that PGF(2 alpha) activates PLD in rat luteal cells. U-73122, a phospholipase C (PLC) inhibitor, and staurosporine, a protein kinase C (PKC) inhibitor, did not inhibit PGF(2 alpha)-stimulated [H-3]PtdEt a ccumulation These results suggest that PGF(2 alpha)-induced PLD activa tion is different from PLC-PKC systems. We reported previously that PG F(2 alpha) stimulated the release of arachidonic acid. The effects of indomethacin, nordihydroguaiaretic acid (NDGA), and 5,8,11,14-eicosate traynoic acid (ETYA), inhibitors of arachidonic acid metabolism, on PG F(2 alpha)-stimulated PtdEt accumulation were examined. Pretreatment w ith indomethacin enhanced PGF(2 alpha)-induced PtdEt accumulation. In contrast, pretreatment with NDGA and ETYA inhibited PGF(2 alpha)-induc ed PtdEt accumulation. It is suggested that PGF(2 alpha)-stimulated PL D activation is mediated via lipoxygenase products.