Prostaglandin synthesis regulation in human amnion tissue: involvement of protein kinase C and dependence on ribonucleic acid and protein synthesis.

Abstract

The role of protein kinase C (PKC) in the control of prostaglandin production by the human amnion was studied. Amnion membranes delivered spontaneously at term were minced and treated with phorbol esters, protein kinase inhibitors, cycloheximide, and actinomycin D; prostaglandin E2 (PGE2) output then was determined. Untreated tissue produced 3.97 +/- 1.13 ng PGE2/micrograms DNA/14 h (mean +/- SEM, n = 19). Phorbol dibutyrate and 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated PGE2 output up to 20-fold in a concentration-dependent manner with potencies corresponding to their efficacy as PKC activators. Four-beta-phorbol and 4-methoxy-TPA, which do not stimulate PKC, did not affect PGE2 output. Stimulation by TPA was blocked by staurosporine (IC50 = 57 nM) and H7; however, these PKC inhibitors did not decrease basal prostaglandin production. Cycloheximide inhibited basal and TPA-promoted PGE2 production and amino acid incorporation. Actinomycin D abolished TPA stimulation without decreasing unstimulated prostaglandin synthesis. These results show that amnion PGE2 production after labor is not maintained by PKC action, but PKC activation in this tissue causes a protein synthesis-dependent and RNA synthesis-dependent increase of PGE2 output. However, basal PGE2 production is dependent upon protein synthesis which, presumably, utilizes pre-existing mRNAs.