[Prostaglandin interaction in the human liver].

The binding of prostaglandin (PG) E1 and Iloprost, a chemically stable PGI2-analogue, to purified plasma cell membranes (LPZM) from liver tissue samples obtained at surgery revealed heterogeneity of the binding sites identifying high and low affinity subpopulations. In contrast to these findings only high affinity binding sites were characterized for PGE2. Displacement studies exhibited the highest competition for the PGE1-sites by PGE1 and subsequently by PGE2, Iloprost, PGD2 and PGF2 alpha. The binding of PGE2 to the hepatic receptor could be best displaced by PGE2 and subsequently by PGE1 and Iloprost, PGD2 and PGF2 alpha. In addition, PGE1, PGE2 and Iloprost enhanced cAMP-production dose-dependently over baseline. Clinical studies revealed a remarkably lower binding capacity for PGE1 in hepatocellular cancer tissue than in normal liver parenchyma. The different binding behaviour of PGE1 (Iloprost) and PGE2 for the first time provides evidence that PGE1 and PGI2 like at platelet membranes occupate the same receptor also at human LPZM. Since a reasonable number of binding sites for these substances and an enhanced cAMP-production were shown in the liver, the study indicates a regulatory role of PGs in hepatic function.