Stimulation of DNA synthesis and proliferation by prostaglandins in primary cultures of adult rat hepatocytes

We studied the effects of several prostaglandins on DNA synthesis and proliferation in serum-free primary cultures of adult rat hepatocytes. Maintained in short-term cultures (i.e., 3.5 h), the hepatocyte parenchymal cells synthesized DNA and proliferated in the presence of various prostaglandins in a dose-dependent manner. The half-maximal effective concentrations (ED50) of prostaglandin F-2 alpha, prostaglandin E-1, prostaglandin E-2 and prostaglandin I-2 for proliferation were estimated to be 1.7 X 10(-9), 2.3 X 10(-8), 2.7 X 10(-8) and 3.3 X 10(-9) M, respectively. Prostaglandin E-2 and prostaglandin I-2 produced greater maximal responses than did either prostaglandin E-1 or prostaglandin F-2 alpha. The cells responded only weakly to prostaglandin D-2. The stimulatory effects of 10(-6) M prostaglandin E-1 and 10(-6) M prostaglandin E-2 on hepatocyte DNA synthesis and proliferation were inhibited by a specific antagonist of the EP1 receptor, 8-chlorodibenz[b, f][1, 4]oxazepine-10(11H)carboxylic acid, 2-[3-[(2-furanylmethyl)-thio]-1-oxopropyl]hydrazide (SC-51322; 10(-6) M). Specific inhibitors of signal transducing elements (e.g., 1-[6-[17 beta-3-methoxyestra-1, 3, 5(10)-trien-17-yl]amino] hexyl]-1H-pyrrol-2,5-dione (U-73122); 10(-6) M), 10(-6) M verapamil, 5 X 10(-6) M genistein) almost completely blocked the growth-promoting effects of the prostaglandins. These results suggest that prostaglandins stimulate hepatocyte DNA synthesis and proliferation by their own receptors and exert their effects through both phospholipase C/Ca2+ and receptor tyrosine kinase pathways. (C) 2000 Elsevier Science B.V. All rights reserved.