Cellular mechanisms for orthovanadate-, phorbol ester-, and calcium ionophore-stimulated prostaglandin production in brook trout (Salvelinus fontinalis) follicles.

Previous studies have shown that prostaglandin (PG) production in brook trout (Salvelinus fontinalis) follicles can be stimulated by sodium orthovanadate, phorbol-12 myristate 13-acetate ester (PMA), and the calcium ionophore, A23187. In the present study, the mechanisms by which these activators stimulate PG production in follicles were specifically investigated by examination of their effects on the release of 3H-labeled arachidonic acid (AA) from prelabeled follicles (AA release) and on the capacity to convert exogenous 3H-AA into prostanoids (AA conversion) by follicle walls. The release of AA from follicles was significantly stimulated by orthovanadate and A23187 after 4 h of incubation. Although AA release was not stimulated by PMA alone, levels of AA release in incubations with both PMA and A23187 were greater than in those with A23187 alone. In contrast, AA conversion in follicle walls was significantly increased by PMA and orthovanadate but not by A23187 alone. The results showed that 1) the calcium ionophore A23187 stimulated ovarian PG production mainly through its effects on the release of AA from follicles; 2) PMA enhanced follicular PG production through an increase in AA conversion in the follicle walls; and 3) orthovanadate mediated PG production by increasing both AA release and AA conversion. In addition, PMA-, A23187-, and orthovanadate-stimulated increases in AA release or conversion were significantly reduced by the translational inhibitor, cycloheximide, and the transcriptional inhibitor, actinomycin. These results indicate that PMA-, A23187-, and orthovanadate-stimulated AA release and AA conversion require protein synthesis and pretranslational activation in the follicles.(ABSTRACT TRUNCATED AT 250 WORDS)