Quantification of NADPH: cytochrome P-450 reductase in liver microsomes by a specific radioimmunoassay technique.
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.
D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology; D007106:Immune Sera / Q000276:immunology; D005779:Immunodiffusion; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000201:enzymology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000276:immunology / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D011863:Radioimmunoassay / Q000379:methods*; D051381:Rats; D011919:Rats, Inbred Strains; D019324:beta-Naphthoflavone
D001571:Benzoflavones; D007106:Immune Sera; D019324:beta-Naphthoflavone; D009251:NADPH-Ferrihemoprotein Reductase; D010634:Phenobarbital