Primary cultures of human hepatocytes but not HepG2 hepatoblastoma cells are suitable for the study of glycosidic conjugation of bile acids

Abstract

To define the role of glycosidic conjugation of bile acids in humans, an in vitro model system is desirable. We studied the formation of glycosidic conjugates of bile acids in primary cultures of human hepatocytes, isolated from organ donor liver, and the human hepatoblastoma cell line, HepG2. Cells were incubated with 100 μM bile acids (chenodeoxycholic, CDCA; hyodeoxycholic, HDCA; and isoursodeoxycholic acids, isoUDCA) and 1–2 mM uridine diphosphoglycosides (UDP-glucose, UDP-Glc; UDP-glucuronic acid, UDP-GlcA, and UDP- N-acetylglucosamine, UDP-GlcNAc), and octyl glucoside. Media were analysed by electrospray-/gas chromatography-mass spectrometry and electrospray with collision induced dissociation. Primary cultures of human hepatocytes formed glycosidic bile acid conjugates with UDP-sugars (6α-Glc-HDCA, 6α-GlcA-HDCA, and 7β-GlcNAc-isoUDCA) and octyl glucoside as sugar donors (3α-Glc-CDCA). HDCA was completely metabolised to either Glc-HDCA, a compound yet not found in vivo, or GlcA-HDCA. No glycosidic bile acid conjugate was found in media from experiments with HepG2. Thus, primary cultures of human hepatocytes, but not HepG2, are suitable in vitro systems for the study of glycosidic bile acid conjugation reactions.