Follicle-stimulating hormone-induced phospholipase A2 activity and eicosanoid generation in rat Sertoli cells.

ABSTRACT

The possibility that FSH stimulates the phospholipase A2 (PLA2) pathway was studied in cultured immature Sertoli cells. FSH induced [3H]-arachidonic acid (AA) release from prelabeled cells in a time- and concentration-dependent fashion (ED50 = 21.8 +/- 1.9 ng/ml). This response could be fully prevented by pretreatment of cells with the PLA2 inhibitor, mepacrine. That PLA2 was the main enzyme responsible for cleavage of AA from membrane phospholipids was directly shown by PLA2 activity assay using vesicles of radiolabeled phosphatidylcholine (PC) as substrate. Furthermore, FSH stimulated eicosanoid generation in a time-dependent manner through the cyclooxygenase but not the lipoxygenase pathway. In fact, higher levels of prostaglandin (PG) E2, F2 alpha, and the stable products of PGI2 and thromboxane A2 (6-keto PGF1 alpha and thromboxane B2, respectively) were generated by the gonadotropin-treated cells as compared to control cells. The effect was inhibited by mepacrine, further supporting the pivotal role of PLA2 in the release of the eicosanoid precursor, AA. Finally, the effect of the main product of FSH-induced AA metabolism, i.e., PGE2, was studied. Intracellular cAMP accumulation in Sertoli cells was stimulated by the prostanoid in a dose-dependent manner (ED50 = 2.3 +/- 0.37 nM). PGE2 also significantly stimulated aromatase activity, a specific marker of Sertoli cell functions, measured as 17 beta-estradiol production (ED50 = 4.7 +/- 0.8 nM). Similar results were obtained with PGF2 alpha. Our findings show that FSH, through the activation of PLA2, leads to AA release with consequent metabolism by the cyclooxygenase pathway.(ABSTRACT TRUNCATED AT 250 WORDS)