Expression and regulation of drug metabolizing enzymes in an immortalized rat hepatocyte cell line.
A hepatic cell line has been immortalized after simian vacuolating virus 40 infection of adult rat hepatocytes maintained in defined culture conditions. This cell line, designated SVHep B4, expressed nuclear large T antigen, exhibited an extended lifespan (50 subcultures) and had a hepatocyte-like morphology. Expression and regulation of drug metabolizing enzymes were studied in long-term cultures of SVHep B4 cells. Significant activities of phase I and phase II enzymes were detected. gamma-Glutamyltransferase, a marker often increased in neoplastic and dedifferentiated hepatocytes, showed a low activity whereas the hepatospecific enzyme tyrosine aminotransferase was expressed at levels similar to those in liver. Responsiveness of drug metabolizing enzymes to inducers was investigated with phenobarbital, dexamethasone and methylcholanthrene. IIB and IA subfamilies of cytochrome P450 were increased, respectively, by phenobarbital (170%) and methylcholanthrene (500%). Glucuronidation of 1-naphthol was increased by phenobarbital (140%) and 3-methylcholanthrene (160%). Phenobarbital, methylcholanthrene and dexamethasone were found to increase significantly gamma-glutamyltransferase while tyrosine aminotransferase activity was enhanced by dexamethasone. Stable expression and inducibility of drug metabolizing enzymes in long-term cultures of the SVHep B4 cell line demonstrate that immortalization of adult hepatocytes represents a promising tool for drug biotransformation studies in vitro.
Centre du Médicament, URA CNRS 597, Faculté des Sciences Pharmaceutiques et Biologiques, Nancy, France.
J
J
Bayad
D
D
Bagrel
N
N
Sabolovic
J
J
Magdalou
G
G
Siest
D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line / Q000201:enzymology; D002472:Cell Transformation, Viral; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D003907:Dexamethasone / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D010088:Oxidoreductases / Q000096:biosynthesis; D010634:Phenobarbital / Q000494:pharmacology; D010641:Phenotype; D051381:Rats; D011919:Rats, Inbred Strains; D013539:Simian virus 40 / Q000201:enzymology; D014444:Tyrosine Transaminase / Q000096:biosynthesis; D005723:gamma-Glutamyltransferase / Q000096:biosynthesis
D008748:Methylcholanthrene; D003907:Dexamethasone; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1; D005723:gamma-Glutamyltransferase; D014444:Tyrosine Transaminase; D010634:Phenobarbital