Evidence that arachidonic acid influences hen granulosa cell steroidogenesis and plasminogen activator activity by a protein kinase C-independent mechanism.
We recently proposed that arachidonic acid serves as a second messenger within granulosa cells from the largest preovulatory follicle of the hen. The present studies were conducted to determine whether the inhibitory effects of arachidonic acid on LH-induced cAMP accumulation and on the ability of cells to convert 25-hydroxycholesterol to progesterone are mediated via the protein kinase C pathway. Furthermore, we determined the effects of arachidonic acid on plasminogen activator activity in granulosa cells. In the first experiment, the putative protein kinase C inhibitor, staurosporine, completely reversed the inhibitory effects of phorbol 12-myristate 13-acetate (PMA) on LH-promoted cAMP formation, but failed to overcome the inhibitory effects of arachidonic acid. Prolonged pretreatment (18 h) with 1.6 microM PMA depleted granulosa cells of both cytosolic and membrane-associated protein kinase C, and subsequently attenuated the inhibitory effects of PMA on LH-induced progesterone production; however, such depletion did not alter the inhibitory effects of phospholipase A2 (PLA2; an agent that increases intracellular levels of arachidonic acid). PMA, but not arachidonic acid, caused a rapid (within 2 min) translocation of protein kinase C from the cytosol to the membrane (a characteristic of agents that activate protein kinase C). Finally, both arachidonic acid and PLA2 inhibit plasminogen activator (PA) activity in a dose-dependent fashion, whereas activation of protein kinase C with PMA stimulates PA activity. Taken together, the data suggest that the effects of arachidonic acid in granulosa cells can occur independently of protein kinase C activation.(ABSTRACT TRUNCATED AT 250 WORDS)
Johnson
A L
AL
Department of Animal Sciences, Rutgers, State University of New Jersey, New Brunswick 08903.
Tilly
J L
JL
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology*; D002645:Chickens; D000242:Cyclic AMP / Q000096:biosynthesis; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000494:pharmacology; D010960:Plasminogen Activators / Q000378:metabolism; D011374:Progesterone / Q000096:biosynthesis; D011493:Protein Kinase C / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001095:Arachidonic Acids; D016718:Arachidonic Acid; D011374:Progesterone; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D011493:Protein Kinase C; D010960:Plasminogen Activators; D013755:Tetradecanoylphorbol Acetate