Preservation and inducibility of xenobiotic metabolism in long-term cultures of adult rat liver cell aggregates.
Liver cell aggregates were established from freshly isolated adult rat hepatocytes and non-parenchymal liver cells (NPC) in rotating cultures. One-third of the inoculated cells formed spheroidal aggregates and one-third of the aggregates remained in culture for up to 12 days, expressing a high intracellular lactate dehydrogenase (LDH) activity and ATP content. The 7-ethoxyresorufin O-deethylase (EROD) activity was doubled on day 8 compared with that in freshly isolated cells, and the glutathione S-transferase (GST) activity was preserved to initial level at day 12. Cytochrome P-450 (CYP) isoforms were differentially affected: at day 8, CYP1A1/2 and CYP2B1/2 contents were close to freshly isolated cell contents; CYP3A1/2 and 4A1/2/3 were preserved at half of the original levels; CYP2C6 and 2C11/2B1/2 were reduced. Enzyme inductions were effective throughout the whole culture period: EROD activity increased fivefold after exposure to phenobarbital (PB) and up to 20-fold after 3-methylcholanthrene (3-MC) exposure; GST activity was stimulated approximately twofold by both inducers. Compound-specific inductions were found for aldrin epoxidase (by PB only), ethoxycoumarin O-deethylase (ECOD) and UDP-glucuronyltransferase (by 3-MC only). Experiments with hepatocyte aggregates showed that the NPC in heterotypic aggregates preserve liver-specific functions more efficiently in long-term experiments. Accordingly, these aggregate cultures from adult rat liver cells could serve as a suitable in vitro model for long-term studies on xenobiotic metabolism or on the interaction of hepatotoxic chemicals with the cross-talk between hepatocytes and NPC.
Ammann
P
P
Institute of Toxicology, Swiss Federal Institute of Technology and University of Zurich, Schorenstrasse 16, CH-8603 Schwerzenbach, Switzerland.
Maier
P
P