Abstract
Induction of coumarin 7-hydroxylation, catalyzed by CYP2A5 in mice and CYP2A6 in humans by various known in vivo murine inducers and modifiers, was compared in human and mouse hepatocytes in culture. Phenobarbital and rifampicin were efficient inducers (up to 10-fold induction) after 48-h treatment in murine cultured hepatocytes, whereas the enzyme activity in human hepatocytes was much more refractory to induction. However, a prolongation of incubation time to 72 h in human hepatocytes led to a modest restoration of inducibility by phenobarbital. Of the three porphyrinogenic inducers studied, griseofulvin induced the murine enzyme efficiently, but not the human enzyme, whereas aminotriazole and thioacetamide had no effect on either species. Pyrazole produced substantial induction in both human and murine hepatocytes, whereas cobalt chloride, which is also an in vivo inducer of the mouse enzyme, had no effect. Clofibric acid, an in vivo depressor of coumarin 7-hydroxylase, also depressed hepatocyte activities. In both murine and human hepatocytes, changes in CYP2A5/6 mRNA levels correlated roughly with enzyme changes, except in the case of cobalt chloride, which increased mRNA levels despite a lack of effect on enzyme activity. In general, human and mouse hepatocytes gave a similar response to CYP2A inducers. However, some differences were found, which means that, although CYP2A isozymes are probably regulated in a similar manner in both species, it is necessary to be cautious before extrapolating to human the results found in mouse models.
Footnotes
-
Send reprint requests to: Maria Jose Gómez-Lechón, Unidad de Hepatologı́a Experimental, Centro de Investigation, Hospital Universitario La Fe, Avda. Campanar 21, Valencia E-46009, Spain. E-mail: Gomez_mjo{at}gva.es
-
This work was supported by grants from the Emil Aaltonen Foundation, the ALIVE Foundation, and the EU-Biomed2 program of European Commission (“EUROCYP”). The study was performed within the framework of the Action COST B1.
- Abbreviations used are::
- ITS
- insulin-transferrin-selenate media supplement
- CYP
- cytochrome P-450
- COH
- coumarin 7-hydroxylase
- FCS
- fetal calf serum
- MTT
- 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide
- PCR
- polymerase chain reaction
- Received May 19, 2000.
- Accepted July 31, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|