Effects of organic solvents on the activities of cytochrome P450 isoforms,UDP-dependent glucuronyl transferase, and phenol sulfotransferase in humanhepatocytes

We studied the effects of acetonitrile, dimethyl sulfoxide (DMSO), and meth anol (MeOH) in human hepatocytes on cytochrome P450 (CYP) and phase II conj ugation activities: phenacetin O-deethylation (CYP1A2), coumarin 7-hydroxyl ation (CYP2A6), tolbutamide 4-hydroxylation (CYP2C9), S-mephenytoin 4'-hydr oxylation (CYP2C19), dextromethorphan O-demethylation (CYP2D6), chlorzoxazo ne 6-hydroxylation (CYP2E1), testosterone 6 beta -hydroxylation (CYP3A4), a nd umbelliferone glucuronidation and sulfation. The solvents were evaluated at concentrations (v/v) of 0.1, 1, and 2%. Previously cryopreserved human hepatocytes pooled from multiple donors were used as suspension cultures in this study. DMSO was found to inhibit CYP2C9 and CYP2C19, CYP2E1, and CYP3 A4 in a concentration-dependent manner. At 2% DMSO, the activities for the four isoforms were approximately 40% (CYP2C9), 23% (CYP2C19), and 11% (CYP2 E1) of that observed for 0.1% acetonitrile and 45% (CYP3A4) of that observe d for 1% acetonitrile. No apparent inhibitory effects were observed for the other activities evaluated. Methanol was found to inhibit CYP2C9 and CYP2E 1 activities, but to a lesser extent than DMSO. Acetonitrile had no apparen t effects on any of the on any of the activities evaluated. These findings should be considered when choosing an organic solvent for metabolism studie s with human hepatocytes.