Effects of ethanol on parietal cell membrane phospholipids and proton pump function

Abstract

The effects of ethanol on membrane phospholipids of isolated rabbit parietal cells (PC) and fundic glands (FG) were evaluated by using proton nuclear magnetic resonance spectroscopy (NMR). The most conspicuous resonance bands in PC and FG spectra at 3.2 and 0.9 ppm were due to the protons of +N(CH3)3 groups of phosphatidylcholine and, to a lesser degree, other phospholipid derivatives and terminal -CH3 groups for all phospholipids, respectively. Ethanol treatment (1 min) of PC and FG at 37 degrees C significantly increased the peak intensity of -CH3 groups in a dose-dependent manner, while no intensity change in PC and a lesser change in FG were observed for the +N(CH3)3 groups, suggesting a greater disorganizing effect of ethanol in the inner hydrophobic (-CH3) compared with the outer hydrophilic [+N(CH3)3] membrane moieties of phospholipids. Ethanol at concentrations greater than 5% (vol/vol) inhibited K+-stimulated paranitrophenyl phosphatase activity of intact PC, which correlated with inhibition of basal and histamine-stimulated aminopyrine uptake ratio by PC and FG. NMR is a sensitive, noninvasive probe to show ethanol-induced changes in intact PC lipid membrane organization without altering ultrastructural morphology.