Phorbol esters and diacylglycerols amplify bradykinin-stimulated prostaglandin synthesis in Swiss 3T3 fibroblasts. Possible independence from protein kinase C.

When Swiss 3T3 fibroblasts were incubated with bradykinin, prostaglandin E2 (PGE2) synthesis was stimulated. Phorbol esters or the diacylglycerol analog 1-oleoyl-2-acetylglycerol (OAG), by themselves, did not acutely stimulate PGE2 synthesis. However, when cells were preincubated with phorbol esters or OAG, bradykinin-stimulated PGE2 synthesis was potentiated markedly. When phorbol esters and OAG were added together, bradykinin-stimulated PGE2 synthesis was potentiated in an additive manner. When cells were preincubated for 48 h with phorbol esters, then bradykinin added, amplification of bradykinin-stimulated PGE2 synthesis by phorbol ester or OAG was still apparent, even though prolonged pretreatment with phorbol esters abolished protein kinase C (Ca2+/phospholipid-dependent enzyme) activity in cell-free preparations. Further, the protein kinase C antagonist, H-7, only slightly inhibited phorbol ester or OAG amplification of bradykinin-stimulated PGE2 synthesis. The possibility is raised that diacylglycerol, formed in response to many receptors, may serve as a transducer of receptor-receptor interactions. Since desensitization or inhibition of protein kinase C only partially reduced the amplification of bradykinin-stimulated PGE2 synthesis by phorbol esters or OAG, the possibility is raised that diacylglycerol mimetics may have actions in addition to activation of protein kinase C.