By combining native polyacrylamide gel electrophoresis (PAGE) and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining, a simple method for detecting NADPH-cytochrome P450 reductase in tissue samples was established. When rat liver microsomal fractions were examined by this method, several bands with different mobility were visualized. Western blot analysis indicated that the band which appeared in the most anodal position among them represented NADPH-cytochrome P450 reductase. SDS-PAGE/Western blot analysis revealed that the molecular weight of the protein forming the band was around 80 kDa, which was identical to that of rat NADPH-cytochrome P450 reductase. The intensity level of NADPH-diaphorase staining assigned to this enzyme estimated by this method increased four times in microsomal fractions prepared from rat fed ethanol chronically compared to that from controls. When a dilution series of a rat liver microsomal fraction was examined by this method and SDS-PAGE/Western blot analysis, their staining intensities representing this enzyme were significantly correlated with each other. Using the naive PAGE/NADPH-diaphorase staining method, NADPH-cytochrome P450 reductase is detected in rat liver microsomes. This method is beneficial because compared with the conventional SDS-PAGE/Western blot analysis, the quantification of NADPH-cytochrome P450 reductase in tissue samples is allowed to be more easily done.
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