Membrane effects of ethanol: bulk lipid versus lipid domains.

It has been well-established that ethanol fluidizes the bulk lipid of membranes and that this effect may alter cell function and be involved in ethanol sensitivity and tolerance. This hypothesis has been supported in several studies, however, there is also a considerable amount of data that do not support such an explanation, e.g., direct effect of ethanol on proteins, other membrane acting drugs, temperature effects, effects of ethanol on aged membranes and inconsistent effects of chronic ethanol consumption on lipid content. This review examined the bulk membrane fluidization hypothesis in light of those data and proposed a modification of the bulk membrane hypothesis that is based on recent data that show that ethanol and other alcohols have a specific effect on the structural properties of different membrane domains. This specific effect of ethanol is discussed within the context of how changes in fluidity of domains may alter membrane function.