Characterization of the induction of rat microsomal cytochrome P450 by tacrine

The effect of multiple-dose tacrine (THA) administration at 2 and 20 mg/kg (single oral doses for 2 weeks) on cytochrome P450 (CYP) was examined in male and female Wistar rats. Changes in CYP were determined by measuring total spectral CYP, the rates of ethoxy- and pentoxyresorufin dealkylations, and the protein expression of several CYPs by western blot analysis of liver microsomes. Animals treated with beta-naphthoflavone or phenobarbital were employed as positive controls. No physiological or metabolic changes were observed in male or female rats treated with 2 mg/kg THA for 2 weeks. Male and female animals treated with 20 mg/kg THA for 2 weeks demonstrated increased CYP1A activity (increased ethoxyresorufin deethylase activity) and increased expression of CYP1A1 with only minor increases in CYP1A2 expression. Compared with the effects of beta-naphthoflavone induction of CYP1A, the induction observed with THA at 20 mg/kg was considered minor.