MAINTENANCE OF TOTAL CYTOCHROME-P-450 CONTENT IN RAT HEPATOCYTE CULTURE AND THE ABUNDANCE OF CYP1A2 AND CYP2B1/2 MESSENGER-RNAS

mRNAs encoding cytochrome P-450s CYP1A2 and CYP2B1/2 have been quantified in rat hepatocytes cultured for periods up to 72 h under several different culture conditions that maintain total cytochrome P-450 content. When hepatocytes were cultured at either 37 or 30-degrees-C in Williams E media, both CYP1A2 and CYP2B1/2 mRNAs declined dramatically. However, when cultured at 30-degrees-C for 24 h, the decline in these mRNAs was not as great as that observed in cells grown at 37-degrees-C. The addition of dimethyl sulphoxide to cells grown at 37-degrees-C did not affect the rate of disappearance of the CYP1A2 or CYP2B1/2 mRNAs. These mRNAs also declined rapidly in cells grown in `P-450 medium' i.e. RPMI 1640 medium without cyst(e)ine but supplemented with 0. 1 mm-delta-aminolaevulinic acid. However, the levels of CYP2B1/2 mRNAs were maintained when hepatocytes were cultured in Williams E medium supplemented with 0.5 mm-metyrapone. These conditions did not, however, maintain the levels of CYP1A2 mRNA.