XENOBIOTIC-METABOLIZING ENZYMES IN PIG NASAL AND HEPATIC TISSUES

1. A study of xenobiotic-metabolizing enzyme activity of the olfactory and respiratory epithelium in the pig was undertaken. The results ind icated that porcine olfactory mucosa contains all the components of th e P450 system. 2. Monooxygenase activities were much higher in olfacto ry than in respiratory microsomes, and the olfactory activities depend ent on CYP2A were higher than those in the liver. By contrast, the olf actory monooxygenases associated with CYP2E1 were poorly or not detect ed, whereas CYP2G1 and a protein immunorelated to CYP1A2 were expresse d in the olfactory epithelium. 3. The activities of several non oxidat ive enzymes (glutathione S-transferase, UDP-glucuronyl transferase, ep oxide hydrolase, DT-diaphorase, benzaldehyde and propionaldehyde dehyd rogenases, and various esterases) were also determined in porcine tiss ues and were found to be higher in the olfactory than in the respirato ry mucosa, but lower or similar to those in liver. 4. An unexpected fi nding was a higher activity of olfactory UDP-GT compared with that of liver when 1-naphtol but not p-hydroxybiphenyl (a good substrate for a specific olfactory UDP-GT(olf) in bovine and rat) was used as substra te, suggesting a porcine specific expression of UDP-GT isoforms. 5. Th e results taken together indicate that the olfactory epithelium of mam mals has a similar cytochrome P450 profile with the CYP2A and CYP2G1 a s dominant isoforms, whereas the olfactory non-oxidative enzymes appea r qualitatively and quantitatively expressed to different extents.