Fluidity of the microsomal membrane and cytochrome P450 reduction kinetics of pig liver microsomes as a consequence of organic solvent impact.
1. The effect of the aromatic solvents toluene, xylene and ethylbenzene on microsomal membrane fluidity and anaerobic NADPH-reduction kinetics were studied. 2. The relation of membrane fluidity to the kinetics of cytochrome P450 reduction by NADPH-cytochrome P450 reductase was examined with regard to a membrane-mediated molecular organization of the multienzyme components of the monooxygenase system. 3. Membrane fluidity changes were detected with the steady-state pyrene excimer formation method and with fluorescence lifetime measurements after incubation of the microsomes with organic solvents. 4. Increase in membrane fluidity in presence of organic solvents leads to a small but significant decrease of the rate constant of the cytochrome P450 reduction kinetics and a change in the relative amplitudes of the components of the biphasic response. 5. The results support the idea of a molecular organization of cytochrome P450 in clusters. Fluidization of the microsomal membrane by organic solvents increase the cytochrome P450 cluster formation.
Engelke
M
M
Biophysical Department, University of Bremen, Germany.
Bergmann
U
U
Diehl
H A
HA
D000818:Animals; D001555:Benzene Derivatives / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects* / Q000378:metabolism; D007425:Intracellular Membranes / Q000187:drug effects* / Q000201:enzymology*; D007700:Kinetics; D008560:Membrane Fluidity / Q000187:drug effects*; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology*; D012997:Solvents / Q000494:pharmacology*; D013552:Swine
D001555:Benzene Derivatives; D012997:Solvents; D003577:Cytochrome P-450 Enzyme System