Comparison of Effects of Propofol, Sevoflurane and Isoflurane on Lipid Membrane Fluidity at Clinical Concentrations

In this study, the effects of anesthetic drugs propofol and sevoflurane on lipid membrane fluidity are compared with isoflurane. To get a basic picture, the simplest lipid membrane of DPPC and red blood cells were chosen. Lipid membranes were labeled with dipyrene-PC fluorescent probe, whose excimer/monomer (E/M) fluorescence peak ratio showed an immediate increase after adding the drugs, indicating a sharp increase of membrane fluidity. We studied clinical concentrations of 10 µM propofol, 0.5 mM sevoflurane and 1 mM isoflurane. The fluidity increases at these concentrations on DPPC lipid bilayer are comparable, and all drugs are quite effective to loosen up the highly ordered lipid domains of saturated lipids. Furthermore, washed human red blood cells were labeled with TMA-DPH fluorescent probe and fluorescence anisotropy measurements were carried out. At clinical concentrations, the decreases of anisotropy were similar for isoflurane and sevoflurane, and the effects are more than that of 174 mM ethanol, which is ten times the legal alcohol limit level in human blood. All these findings depict that propofol, sevoflurane and isoflurane at clinical concentrations have similar effects on membrane systems, and significantly and rapidly increase membrane fluidity.