Identification of prostaglandin E metabolites from primary cultures of rat hepatocytes.

Primary cultured rat hepatocytes were shown to bind to prostaglandins E1, E2, D2 and F2 alpha and then rapidly degrade at 37 degrees C. 6-Ketoprostaglandin F1 alpha and thromboxane B2, which are inactive metabolites of prostaglandin I2 and thromboxane A2, respectively, bound less effectively to the cells and were not degraded. Incubation of hepatocytes with 3H-labeled prostaglandins, treatment of the cells at an acidic pH, and analysis of the acid solution by thin-layer chromatography, showed that the radioactive material was bound to the cell surface and consisted of intact prostaglandin and its metabolites. The metabolites of prostaglandin E that accumulated in the culture medium were purified by silicic acid column and silica gel thin-layer chromatographies, and analyzed by gas chromatography-mass spectrometry. Prostaglandins E1 and E2 gave exactly the same metabolites, which were identified as dinorprostaglandin E1 and tetranorprostaglandin E1, representing products of beta-oxidation. These data suggest that part of the carboxyl side chain of prostaglandins, but not of inactive metabolites, was eliminated by a beta-oxidation system in the hepatocytes, while the rest of the molecule was not degraded appreciably and was rapidly transferred to the outside of the cells.