Prostaglandins induce proliferation of rat hepatocytes through a prostaglandin E(2) receptor EP(3) subtype

We characterized the proliferative action of prostaglandins (PGs) in relation to their membrane receptors on rat hepatocytes in primary culture. PGs in the order 16,16-dimethyl PGE(2) > PGE(2) > PGF(2 alpha) > PGD(2). augmented epidermal growth factor (EGF)/insulin-induced DNA synthesis, assessed by [H-3] thymidine incorporation, in a concentration-dependent manner, whereas PGs alone did not stimulate basal DNA synthesis without EGF and insulin. The cells exhibited [H-3]PGE(2) binding sites that were displaced by unlabeled PGs in the order PGE(1) = PGE(2) > PGF(2 alpha) > PGD(2). PGE(2) inhibited glucagon-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) accumulation concentration dependently. The mean effective concentration for DNA synthesis, median inhibitory concentration for cAMP accumulation, and dissociation constant for [H-3]PGE(2) binding at 25 degrees C were almost identical (similar to 70 nM). Treatment of the cells with pertussis toxin (100 ng/ml), which ADP-ribosylated mast of the 41-kDa substrate, abolished the proliferative effects of PGs. We detected the expression of mRNA of the EP(3) subtype PGE(2) receptor using reverse transcription-polymerase chain reaction. Moreover, an EP(3) agonist, enprostil, but not the EP(1) agonist 17-phenyl-trinor-PGE(2) or the EP(2)/EP(4) agonist 11-deoxy-PGE(1), stimulated EGF/insulin-induced DNA synthesis. These results indicate that PGs act as comitogenic growth factors through the EP(3) subtype PGE(2) receptor coupled with Gi protein in cultured rat hepatocytes.