CYP1A1 and CYP1B1, Two Hydrocarbon‐Inducible Cytochromes P450, are Constitutively Expressed in Neonate and Adult Goat Liver, Lung and Kidney *

The ontogeny of cytochrome P-450 isozymes (P450) in goat liver, lung and kidney was studied using anion exchange HPLC separation of solublized microsomal proteins and Western immunoblotting. Comparison of the overall HPLC profile of goat P450 isozymes between liver, lung and kidney showed that while the P450's of goat liver were equally separated into five peaks of isozyme(s), only two peaks constitute the majority of P450 isozyme(s) in lung and kidney, thus demonstrating the tissue specific differences in P450 isozyme distribution in goats. Immunoblotting analysis using polyclonal antibodies against rat CYP1B1, and mouse CYP1B1, polyaromatic hydrocarbon-regulated P450's, revealed that goat orthologs of CYP1A1 and CYP1B1 are expressed constitutively in goats. The CYP1A1 was expressed in goat liver and lung as early as 1st day of age, and the levels of its expression in adult lung and liver were, respectively, 1.3 and 5.5 pmol per mg microsomal proteins. CYP1B1 was expressed in goat livers in substantial levels as of 1 week of age and increased thereafter to reach approximately 4.5 pmol per mg microsomal proteins in adult livers, while low level was detectable only in adult but not neonate lung tissues. Furthermore, polyclonal antibodies against rat CYP1A2 detected very high levels of CYP1A2 in livers of adult and 6 week old goats. The Ah receptor which controls the expression of CYP1A1/1A2 and CYP1B1, was detected in cytosolic fractions from these tissues as a 104 kDa and a minor level of the 106 kDa form. These are potentially very important findings in light of the role of CYP1A1/1A2 and CYP1B1 in activation of polyaromatic hydrocarbons, heterocyclic amines and nitroaromatic hydrocarbons to genotoxic metabolites, and the health consequences of these metabolites on humans, as consumers of goat milk and meat. Using polyclonal antibodies against rat hepatic CYP2B1 and CYP3A1, the goat CYP2B and CYP3A forms were not detectable in livers of goats at any age, but lungs of adult and 6 week old goats expressed these two CYPs in levels equivalent to the livers of phenobarbital-induced rats. On the other hand, anti-rat CYP2C6 antibodies specifically detected two goat ortholog forms which were expressed in all three tissues and exhibited age-dependent changes. In conclusion, results from both immunoblot and HPLC analyses confirmed that, as in other species, the expression of P450 isozymes in goat is under both developmental- and tissue-specific regulatory factors.