title: Effects of m-xylene on rat nasal cytochrome P450 mixed function oxidase activities.
abstract: The effect of m-xylene on the rat nasal cytochrome P450 (P450) mixed function oxidase system was analyzed in vitro utilizing microsomes isolated 2, 12, and 24 h following intraperitoneal administration of this solvent in vivo. For comparative purposes, pulmonary and hepatic activities were also measured. Benzyloxyresorufin O-deethylation (BROD) and ethoxyresorufin O-deethylation (EROD), catalytic activities linked with P450 isozymes IIB1 and IA1, respectively, were inhibited in nasal tissue at all times following m-xylene administration. Pulmonary tissue mimicked this m-xylene-dependent inhibition of BROD activity but did not display significant inhibition of EROD activity. In contrast, m-xylene caused a dramatic induction of both BROD and EROD activity in hepatic tissue. The metabolism of a third P450 substrate, cyclopentadienyl manganese tricarbonyl (CMT), was also analyzed. m-Xylene caused significant inhibition of CMT metabolism at all time points in both nasal and pulmonary microsomes but was without effect on hepatic microsomal metabolism of this compound. These data show an inhibitory effect of m-xylene on rat nasal and pulmonary but not hepatic cytochrome P450-dependent metabolism.
authors.affiliation: Toxicology Program, School of Pharmacy, University of Connecticut, Storrs 06269-2092.
authors.forename: K T
authors.initials: KT
authors.lastname: Blanchard
authors.forename: J B
authors.initials: JB
authors.lastname: Morris
mesh_terms: D000818:Animals; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects* / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D008168:Lung / Q000201:enzymology; D008297:Male; D008861:Microsomes / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000187:drug effects* / Q000378:metabolism; D009297:Nasal Mucosa / Q000201:enzymology*; D009942:Organometallic Compounds / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D051381:Rats; D014992:Xylenes / Q000633:toxicity*
chemical_list: D009942:Organometallic Compounds; D014992:Xylenes; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1; C031285:3-xylene; C044679:manganese cyclopentadienyl tricarbonyl