Monoclonal antibody-directed radioimmunoassay of specific cytochromes P-450.
A rapid solid phase radioimmunoassay (RIA) for cytochromes P-450 has been developed utilizing specific monoclonal antibodies to major forms of rat liver cytochrome P-450 that are induced by 3-methylcholanthrene (MC-P-450) and phenobarbital (PB-P-450). Monoclonal antibodies (MAbs) that were endogenously labeled with [35S]methionine were used to detect MAb-specific cytochromes P-450 in liver microsomes from untreated rats and rats pretreated with 3-methylcholanthrene (MC) or phenobarbital. The competitive binding assays are rapid and can detect cytochrome P-450 in less than 100 ng of microsomal protein. The RIA was used to examine the distribution of MAb-specific cytochromes P-450 in extrahepatic tissues of MC-treated rats; an approximately 30- to 50-fold greater amount of MC-P-450 in liver relative to lung and kidney was observed, which corresponds well with aryl hydrocarbon hydroxylase activity in these tissues. The inducibility of MAb-specific cytochromes P-450 in several species was also examined by competitive RIA. Significant increases in the MAb-specific P-450 were observed in MC-treated rats, guinea pigs, and C57BL/6 mice, all highly inducible for aryl hydrocarbon hydroxylase; little increase was observed for the relatively noninducible DBA/2 mouse strain.
D000818:Animals; D000911:Antibodies, Monoclonal; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis* / Q000235:genetics; D006168:Guinea Pigs; D007668:Kidney / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D014018:Tissue Distribution
D000911:Antibodies, Monoclonal; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System