[Interaction of enkephalin with lipid components of cell membranes].
The influence of enkephalin on structural and functional properties of model membranes from cell membrane lipids was investigated. Administration of enkephalin increased the permeability of lecithin and cerebroside membranes for potassium and calcium ions up to three orders. The permeability of the model membranes was discovered to be dependent on enkephalin concentration within the range from 10(-5) to 10(-6) M. Cation specificity, primarily calcium one, of modified lipid membranes was demonstrated. Thermodynamic studies showed that interaction of enkephalin with liposomes was endothermic in nature. The thermal effect of the interaction in the presence of Ca2+ was greater than that in the presence of K+, which is likely to be related to appreciable conformational changes in liposome structure in the environment of calcium. The data obtained suggest that enkephalin is capable of raising the permeability of cell membranes through lipid fractions because of conformational changes in the structure of the membranes under study during their interaction with enkephalin.