Activation of protein kinase C is coupled to prostaglandin F_2α synthesis in the ovary: studies in cultured swine granulosa cells

We have investigated the role of phospholipid-sensitive calcium-dependent protein kinase (protein kinase C) in prostaglandin F_2α synthesis by monolayer cultures of swine granulosa cells. In this system, specific phorbol ester derivatives known to activate protein kinase C significantly augmented the production of prostaglandin F_2α. Phorbol ester in conjunction with the ionophore A23187 synergistically increased prostaglandin F_2α production. 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 F_2α production was concordant with that demonstrated for activation of protein kinase C in the swine ovary. In addition, a nonphorbol stimulator of protein kinase C, l-octanoyl-2-acetylglycerol, also significantly enhanced prostaglandin F_2α biosynthesis. The synthesis of immunoassayable prostaglandin F_2α was confirmed by high-pressure liquid Chromatographie purification of this radiolabeled metabolite of [³H]arachidonic acid. Thus, the present studies indicate that the protein kinase C effector pathway in the swine granulosa cell is functionally coupled to prostaglandin F_2α production.