SPECIES-SPECIFIC INDUCTION OF CYTOCHROME-P-450 4A-RNAS - PCR CLONING OF PARTIAL GUINEA-PIG, HUMAN AND MOUSE CYP4A-CDNAS

PCR was used to demonstrate the presence of a conserved region and to clone novel members of the cytochrome P-450 4A gene family from guinea pig, human and mouse cDNAs. This strategy is based on the sequences a t nucleotides 925-959 and at the haem binding domain (nucleotides 1381 -1410) of the rat CYP4A1 gene. Murine Cyp4a clones showed high sequenc e identity with members of the rat gene family, but CYP4A clones from human and guinea pig were equally similar to the rat/mouse genes, sugg esting that the rat/mouse line had undergone gene duplication events a fter divergence from human and guinea-pig lines. The mouse Cyp4a-12 cl one was localized to chromosome 4 using interspecific backcross mappin g, in a region of synteny with human chromosome 1. The assignment of t he human CYP4A11 gene to chromosome 1 was confirmed by somatic cell hy bridization. An RNAase protection assay was shown to discriminate betw een the murine Cyp4a-10 and Cyp4a-12 cDNAs. Treatment of mice with the potent peroxisome proliferator methylclofenapate (25 mg/kg) induced C yp4a-10 RNA in liver, and to a lesser extent in kidney; there was no s ex difference in this response. Cyp4a-12 RNA was present at high level s in male control liver and kidney samples, and was not induced by tre atment with methylclofenapate. However, Cyp4a-12 RNA was present at lo w levels in control female liver and kidney RNA, and was greatly induc ed in both organs by methylclofenapate. Guinea pigs were exposed to me thylclofenapate (50 mg/kg), but there was no significant induction of the guinea-pig CYP4A13 RNA. These findings are consistent with a speci es difference in response to peroxisome proliferators between the rat/ mouse and the guinea pig.