Effect of Probucol on Cytochrome P450 Activities in Human Liver Microsomes.

Characterization of cytochrome P450‐mediated drug metabolism in cats

“…The CYP activities of cat microsomes are compared with those of dogs (from Kuroha et al. , 2002a,b) and humans (from Umehara et al. , 2002 and Perloff et al.…”

Effect of Nilvadipine, a Dihydropyridine Calcium Antagonist, on Cytochrome P450 Activities in Human Hepatic Microsomes

“…[14][15][16] The incubation mixture consisted of 0.2-1 mg/ml of human microsomes, 2.5 mM NADP ϩ , 25 mM glucose-6-phosphate, 10 mM magnesium chloride, 2 units of glucose-6-phosphate dehydrogenase, 100 mM potassium phosphate buffer (pH 7.4), 0.1 mM EDTA, and 5 ml of methanol or 0.5-4 mM nilvadipine dissolved in methanol in a final volume of 500 ml.…”

Effect of Cefixime and Cefdinir, Oral Cephalosporins, on Cytochrome P450 Activities in Human Hepatic Microsomes

“…15,16) The incubation mixture consisted of human microsomes, 2.5 mM NADP ϩ , 25 mM glucose-6-phosphate, 10 mM magnesium chloride, 2 units of glucose-6-phosphate dehydrogenase, 100 mM potassium phosphate buffer (pH 7.4), 0.1 mM EDTA, and 0.01 ml of 200 mM sodium bicarbonate or 100 mM cefixime or cefdinir dissolved in 200 mM sodium bicarbonate in a final volume of 0.5 ml. 15,16) The microsomal protein concentration in the mixture was 0.2 (for 7-ethoxyresorufin O-deethylation, coumarin 7-hydroxylation, and 7-benzyloxyresorufin O-debenzylation), 0.5 (for tolbutamide methylhydroxylation, nifedipine oxidation, and testosterone 6b-hydroxylation), or 1 mg/ml (for S-mephenytoin 4Ј-hydroxylation, bufuralol 1Ј-hydroxylation, and chlorzoxazone 6-hydroxylation). Concentrations of 7-ethoxyresorufin, coumarin, 7-benzyloxyresorufin, tolbutamide, Smephenytoin, bufuralol, chlorzoxazone, nifedipine, and testosterone were 0.5, 2, 1.5, 400, 100, 20, 100, 30, and 150 mM, respectively; which are around the expected K m .…”

“…Concentrations of 7-ethoxyresorufin, coumarin, 7-benzyloxyresorufin, tolbutamide, Smephenytoin, bufuralol, chlorzoxazone, nifedipine, and testosterone were 0.5, 2, 1.5, 400, 100, 20, 100, 30, and 150 mM, respectively; which are around the expected K m . 15,16) Because cefdinir interfered with the assay of methylhydroxytolbutamide by the methods described previously, 15,16) the effect of cefdinir on the methylhydroxytolbutamide formation was determined as follows. Briefly, after the reaction was terminated by the addition of 1 M HCl, 50 ml of internal standard (20 mg/ml sodium phenobarbital) and 3 ml of ethylacetate/hexane (1 : 1) were added, and the mixtures were shaken for 10 min and centrifuged at 1900 g for 5 min.…”