Membrane fluidity and kinetics of Ca2+-dependent potassium channels

Patch-clamp technique and fluorescence polarization analysis were used to study the effect of lipids on the kinetic of Ca2+-dependent K+ channels and membrane fluidity. Cultured smooth muscle cells from human and rabbit aortas were used. 2-decenoic acid (DA) was applied to increase membrane fluidity and cholesterol (CHS) level was varied using mevinolin (MEV) and CHS-enriching medium. In the presence of 0.5 microM Ca2+ and 2 mM Mg2+ more than 40-fold elevation in the probability of the channels been open (Po) was observed under DA action. Treatment of cells with MEV leads to nearly 2 fold increase in membrane fluidity and to more than 4 times elevation of Po. The addition of CHS to the cell membrane resulted in a nearly 2 fold decrease in membrane fluidity and about 2 fold decrease in Po. The data suggest that lipid content affect the kinetics of Ca2+-activated K+ channels presumably due to changes in membrane fluidity.