Drug metabolism components in liver microsomes from Hypostomus punctatus, a brazilian benthic fish (cascudo)

Abstract 1. The major components of hepatic drug biotransformation system were identified in a Brazilian freshwater benthic fish. 2. Cytochrome P-450 difference spectra were obtained adding 0.02 mM phenazine ethosulphate and 2 mM ascorbate to microsomal suspensions. Basal levels of P-450 were high (0.9 nmol/mg of microsomal protein) and were not induced by 3-MC. 3. Microsomal NADPH-cytochrome C reductase activity was determined in presence of 1.3 × 10 −4 M NADPH, 3.3 × 10 −5 M cytochrome C, 1.0 × 10 − M EDTA, 66 μg of microsomal protein per ml in a 0.3 M Tris-HCl buffer, pH8.6. Basal levels of NADPH-cytochrome C were 152.7nmoles/min/mg of microsomal protein.