Differential effects of cholesterol and lanosterol on artificial membranes (glucose permeability/¹³C nuclear magnetic resonance spectroscopy)

Abstract

The effects of cholesterol, 4,4-dimethylcholesterol, and lanosterol (4,4',14α-trimethyl-δ^8,24-cholestadiene-3β-ol) on some properties of lecithin vesicles have been compared. Unlike cholesterol, lanosterol retards the exit of trapped glucose from phospholipid vesicles only slightly. The ¹³C nuclear magnetic resonance spectrum of cholesterol/lecithin vesicles shows no resonances attributable to the sterol. By contrast, several resonances attributable to quaternary carbon atoms or methyl groups are seen in the ¹³C nuclear magnetic resonance spectrum of lanosterol/lecithin vesicles, indicating that lanosterol is much less immobilized than cholesterol. Because the membrane behavior of 4,4-dimethylcholesterol is closely similar to that of cholesterol, it is concluded that the axial 14-α-methyl group is responsible for the lessened membrane immobilization of lanosterol. The results emphasize the importance of a planar sterol α-face for interaction with phospholipid acyl chains.