Effects of oxygen on the membrane structure and the metabolism of lipophilic nitroxide in rat liver microsomes.

The effects of oxygen on the metabolism of lipophilic nitroxide and the membrane structure of microsomes were investigated with an ESR spectrometer equipped with a hand-made gas-permeable sampling tube. The half life of gas change in the membrane was confirmed to be 48 s by the line-width of the ESR signal. The signal intensity of lipophilic nitroxide in microsomal membranes decreased with NADPH under N2 and increased under O2. The change of signal intensity was reversible, suggesting that lipophilic nitroxide can be used as an indicator of the redox state in membranes for in vivo ESR imaging.