RELATIONSHIP OF ALCOHOL-INDUCED CHANGES IN MG2-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-u ndecyl alcohol), isoamyl alcohol and benzyl alcohol on the activity of membrane enzyme Mg2+-ATPase of the rabbit small intestinal brush bord er membrane. Their relationships with the changes in the fluidity of t he membrane lipid bilayer were examined through studies on the fluores cence anisotropies of diphenylhexatriene (DPH) and its ionic derivativ es. Good linear correlations were found both between the partition coe fficients of the alcohols and their concentrations causing similar dec reases in the activity of Mg2+-ATPase and between their partition coef ficients and the alcohol-induced changes in fluorescence anisotropies. Within the concentration range of the alcohols tested, including isoa myl alcohol and benzyl alcohol, the decreases in activity of the membr ane enzyme Mg2+-ATPase ATPase clearly corresponded with the decreases in fluorescence anisotropy of DPH, which is thought to be located with in the hydrophobic core of the membrane. From these findings, one poss ible explanation is that inhibition of this enzyme by the alcohols is due to perturbation of the lipid bilayer of the brush border membrane.