Relationship of alcohol-induced changes in Mg(2+)-ATPase activity of rabbit intestinal brush border membrane with changes in fluidity of its lipid bilayer.

We examined the effects of seven n-alkyl alcohols (from n-butyl to n-undecyl alcohol), isoamyl alcohol and benzyl alcohol on the activity of membrane enzyme Mg(2+)-ATPase of the rabbit small intestinal brush border membrane. Their relationships with the changes in the fluidity of the membrane lipid bilayer were examined through studies on the fluorescence anisotropies of diphenylhexatriene (DPH) and its ionic derivatives. Good linear correlations were found both between the partition coefficients of the alcohols and their concentrations causing similar decreases in the activity of Mg(2+)-ATPase and between their partition coefficients and the alcohol-induced changes in fluorescence anisotropies. Within the concentration range of the alcohols tested, including isoamyl alcohol and benzyl alcohol, the decreases in activity of the membrane enzyme Mg(2+)-ATPase clearly corresponded with the decreases in fluorescence anisotropy of DPH, which is thought to be located within the hydrophobic core of the membrane. From these findings, one possible explanation is that inhibition of this enzyme by the alcohols is due to perturbation of the lipid bilayer of the brush border membrane.