TY - JOUR
T1 - Diethyl ether as a substrate for acetone/ethanol-inducible cytochrome P-450 and as an inducer for cytochrome(s) P-450
AU - Brady, J. F.
AU - Lee, M. J.
AU - Li, M.
AU - Ishizaki, H.
AU - Yang, C. S.
PY - 1988
Y1 - 1988
N2 - The ability of diethyl ether to serve as a substrate for microsomal and purified cytochrome P-450 (P-450) and as an inducer for rat hepatic microsomal monooxygenase activities was examined. Microsomal oxidation of ether to acetaldehyde, as monitored by high pressure liquid chromatography, was elevated 3- to 5-fold by treatment of rats with acetone or ethanol, 1.5- and 2-fold by treatment with ether, and only slightly by phenobarbital treatment. Ether also induced N-nitrosodimethylamine demethylase by up to 2-fold and 7-pentoxyresorufin dealkylation by up to 10-fold. These trends agreed with immunoblot experiments in which ether was a weak inducer of the P-450 isozyme IIE1 (encoded by the rat gene P450IIE1), but a stronger inducer of IIB1. A monoclonal antibody against IIE1 inhibited the deethylation by 78% in microsomes from acetone-treated rats and by 45% in controls. N-Nitrosodimethylamine, as well as common inhibitors of IIE1 such as hexane, benzene, pyrazole, and phenylethylamine, strongly inhibited ether deethylation. Using microsomes from acetone-induced rats, the apparent K(m) for deethylation was 13.4 ± 2.4 μM and the V(max) was 8.2 ± 0.2 (nmol of acetaldehyde/min/nmol of P-450). The K(m) for the controls was 71.3 ± 9.5 μM. The rates of deethylation at 1 mM ether by purified, reconstituted IIE1 and IIB1 were 4.2 and 0.42 (nmol of acetaldehyde/min/nmol of P-450), respectively. Cytochrome b5 stimulated the rate due to IIE1 apparently by a decrease in the K(m). These findings, along with previous work showing marked inhibition by ether of IIE1-dependend reactions, strongly support a major role for this isozyme in ether metabolism.
AB - The ability of diethyl ether to serve as a substrate for microsomal and purified cytochrome P-450 (P-450) and as an inducer for rat hepatic microsomal monooxygenase activities was examined. Microsomal oxidation of ether to acetaldehyde, as monitored by high pressure liquid chromatography, was elevated 3- to 5-fold by treatment of rats with acetone or ethanol, 1.5- and 2-fold by treatment with ether, and only slightly by phenobarbital treatment. Ether also induced N-nitrosodimethylamine demethylase by up to 2-fold and 7-pentoxyresorufin dealkylation by up to 10-fold. These trends agreed with immunoblot experiments in which ether was a weak inducer of the P-450 isozyme IIE1 (encoded by the rat gene P450IIE1), but a stronger inducer of IIB1. A monoclonal antibody against IIE1 inhibited the deethylation by 78% in microsomes from acetone-treated rats and by 45% in controls. N-Nitrosodimethylamine, as well as common inhibitors of IIE1 such as hexane, benzene, pyrazole, and phenylethylamine, strongly inhibited ether deethylation. Using microsomes from acetone-induced rats, the apparent K(m) for deethylation was 13.4 ± 2.4 μM and the V(max) was 8.2 ± 0.2 (nmol of acetaldehyde/min/nmol of P-450). The K(m) for the controls was 71.3 ± 9.5 μM. The rates of deethylation at 1 mM ether by purified, reconstituted IIE1 and IIB1 were 4.2 and 0.42 (nmol of acetaldehyde/min/nmol of P-450), respectively. Cytochrome b5 stimulated the rate due to IIE1 apparently by a decrease in the K(m). These findings, along with previous work showing marked inhibition by ether of IIE1-dependend reactions, strongly support a major role for this isozyme in ether metabolism.
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M3 - Article
C2 - 3340079
SN - 0026-895X
VL - 33
SP - 148
EP - 154
JO - Molecular pharmacology
JF - Molecular pharmacology
IS - 2
ER -