We have developed a specific radioimmunoassay to quantify NADPH: cytochrome P-450 reductase. The assay is based on the use of 125I-labelled NADPH: cytochrome P-450 reductase as the radiolabelled antigen and can detect quantities of this protein in amounts as low as 30 pg. The results of the radioimmunoassay demonstrates that the 2.7-fold increase in enzyme activity in rat liver microsomal membranes after phenobarbital treatment is due to increased amounts of the protein. beta-Naphthoflavone treatment, however, did not alter the activity or the quantity of this enzyme in microsomes. The quantification of NADPH: cytochrome P-450 reductase in the microsomes isolated from control and phenobarbital- and beta-naphthoflavone-treated animals permits the calculation of the ratio of this protein to that of total cytochromes P-450. A molar ratio of 15:1 (cytochromes P-450/NADPH: cytochrome P-450 reductase) was calculated for control and phenobarbital-treated animals. This ratio increased to 21:1 after beta-naphthoflavone treatment. Thus the molar ratio of these proteins in liver microsomes can vary with exposure of the animals to particular xenobiotics.
Quantification of NADPH: cytochrome P-450 reductase in liver microsomes by a specific radioimmunoassay technique
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E A Shephard, I R Phillips, R M Bayney, S F Pike, B R Rabin; Quantification of NADPH: cytochrome P-450 reductase in liver microsomes by a specific radioimmunoassay technique. Biochem J 1 May 1983; 211 (2): 333–340. doi: https://doi.org/10.1042/bj2110333
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