TABLE 1

Kinetic parameters for nifedipine metabolism catalyzed by hepatic and small intestinal microsomes from B6 and CL mice

Rates of formation of NFPO were determined as described under Materials and Methods. Reaction mixtures contained 25 mM phosphate buffer, pH 7.4, 5 to 50 μM nifedipine, and 0.5 mg/ml microsomal protein. Each microsome preparation was obtained from pooled tissues from two to three mice. Reactions were performed in duplicate in the presence or absence of 1.0 mM NADPH. Rates of product formation were linear with reaction time. The values presented for the apparent K_m and apparent V_max are the means of two independent determinations (with the individual values listed in parentheses), except for CL liver, for which a single microsomal preparation was analyzed.