We have examined the role of phospholipid-sensitive calcium-dependent protein kinase (protein kinase C) in prostaglandin E2 synthesis by monolayer cultures of swine granulosa cells. Specific phorbol ester derivatives known to activate protein kinase C significantly augmented the production of prostaglandin E2. These stimulatory actions were dose and time-dependent, and could be abolished by the cyclooxygenase inhibitor, indomethacin, or the protein synthesis inhibitor, cycloheximide. Moreover, the rank order of potency of phorbol esters in enhancing prostaglandin E2 production was concordant with that demonstrated for activation of protein kinase C. Phorbol ester in conjunction with the divalent cation ionophore, A23187, increased prostaglandin E2 production synergistically. In addition, a non-phorbol stimulator of protein kinase C, 1-octanoyl-2-acetylglycerol, also significantly enhanced prostaglandin E2 biosynthesis. The stimulated synthesis of prostaglandin E2 was confirmed by high-pressure liquid chromatographic purification of this radiolabeled metabolite of 3H-arachidonic acid, and by capillary gas chromatography high-resolution mass spectrometry. Thus, the present studies indicate that the protein kinase C effector pathway is functionally coupled to prostaglandin E2 production in the swine granulosa cell.
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