Hepatocyte-hepatoma cell hybrids. Characterization and demonstration of bile acid synthesis

Efficient in vitro vectorial transport of a fluorescent conjugated bile acid analogue by polarized hepatic hybrid WIF-B and WIF-B9 cells

Efficient transport of bile acids, a typical characteristic of hepatocytes, is partially lost in most hepatoma cell lines and in normal hepatocytes after some days in culture. We have tested whether the polarized rat hepatoma-human fibroblast hybrid WIF (hybrids between W138 and Fao cells) cells previously obtained by our group were able to perform vectorial transport of the fluorescent bile acid derivative cholylglycylamidofluorescein (CGamF) towards the bile canaliculi (BC). Four different WIF clones were analyzed. All were well polarized, as shown by the formation of spherical and even tubular BC-like structures and by the restricted localization at the BC, visualized by immunofluorescence, of the apical membrane marker HA4, a possible bile acid carrier. WIF-B and its subclone WIF-B9 were found to accumulate CGamF in 65% to 75% of their BC. This transport was time, temperature, and partly sodium dependent and was inhibited by coincubation with the parental natural bile salt cholylglycine. Dinitrophenyl glutathione, a substrate of the canalicular multispecific organic anion transporter, did not inhibit CGamF canalicular secretion, whereas it greatly impaired the canalicular secretion of a non-bile acid organic anion, fluorescein, generated intracellularly from fluorescein diacetate. Confocal microscopy confirmed the presence of CGamF in the cytoplasm, supporting a transcellular route from medium to BC. In contrast, two other polarized clones exhibited a poor ability (WIF 12-6) or no ability (WIF12-1 TGdelta) to vectorially transport CGamE In conclusion, WIF-B and WIF-B9 exhibit not only structural but also functional polarity, at least as far as vectorial organic anion transport is concerned.

Xenobiotic-metabolizing enzyme activities in hybrid cell lines established by fusion of primary rat liver parenchymal cells with hepatoma cells

1. The activities of xenobiotic-metabolizing enzymes were determined in hybrid cell lines (hepatocytoma, HPCT) which have been established by fusion of liver parenchymal cells from adult rat (PC) with cells from a Reuber hepatoma cell line (FAO). 2. Cytochrome P450 was not measurable spectrophotometrically in FAO and HPCT. P450-dependent conversion of testosterone was below the detection limit in FAO and only marginally present in HPCT. 3. Microsomal and cytosolic epoxide hydrolase, glutathione S-transferase and phenol sulphotranserase were low or even below detection limit in FAO. These enzyme activities were significantly higher in HPCT and correspond to about 1-10% the activities measured in PC. 4. 1-Naphthol UPD-glucuronosyl transferase activity was about 20% in FAO and about 100% in HPCT compared to PC. 5. Metabolic conversion of benzo[a]pyrene was low in FAO, high in PC, and intermediate in HPCT. The presented data, however, do not allow the conclusion whether this intermediate rate is catalyzed by similar P450 isoenzymes as in PC. 6. Due to the easily measurable phase II-metabolizing enzyme activities HPCT may, however, be useful for in vitro enzyme induction or repression studies.