The interaction of styrene oxide with hepatic cytochrome P-450 in vitro and effects of styrene oxide inhalation on xenobiotic biotransformation in mouse liver and kidney

Vainio, H.; Elovaara, E.

Biochemical Pharmacology 28(13): 2001-2004

1979


ISSN/ISBN: 0006-2952
PMID: 475843
DOI: 10.1016/0006-2952(79)90215-6
Accession: 041679782

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Abstract
Female mice (strain CB-20) were killed 0.5 hr, 18 hr and 5 days after inhaling styrene oxide for 6 hr per day for 3 consecutive days at concentrations of 200, 200 and 100 p. p. m., respectively. Acute intoxication was manifest, both clinically and as a depression of non-protein sulfhydryl content in liver and kidney. During the recovery period of 5 days a transient rise in microsomal 7-ethoxycoumarin O-deethylase activity in both tissues paralleled changes in cytochrome P-450 content. The activity of microsomal epoxide hydratase (measured with styrene oxide as the substrate) was not affected by the treatment, neither was the UDP-glucuronosyltransferase activity. In the presence of hepatic microsomes from phenobarbital-treated mice, styrene oxide produced a characteristic Type I difference spectrum. A comparison of the binding parameters for the interaction of styrene oxide with uninduced and phenobarbital- and 3-methylcholanthrene-induced microsomes indicates that the binding of styrene oxide is catalyzed by more than one type of P-450 hemoprotein. but predominantly by phenobarbital-induced cytochrome P-450. In addition, in phenobarbital-pretreated microsomes styrene oxide had two spectral dissociation constants (Ks), 0.05 m M and 0.4 m M.