[Effect of exposure to "stress" on the electrical properties of BLM]

The influence of high potential and hydrostatic pressure gradients on BLM has been studied. It has been found that short exposures of BLM to the above factors, which are nearly as strong as those rupturing BLM, often induce in the membrane unusual states characterized by drastic increase in the current fluctuations with simultaneous increase of its average value. The level of fluctuations and the average current on individual membranes subjected to intermittent exposures vary appreciably. Of greatest interest are the membranes for which the average current value is not much higher than the background level. Such membranes can fluctuate steadily for several hours without any appreciable change in their behavior. In these cases the minimum current value during fluctuations often corresponds to the background current. Usually the current fluctuations on membranes excited by potential or hydrostatic pressure gradients cease abruptly. The electrical properties of such membranes are virtually the same as those of the unstressed membranes. The qualitative studies of the influence of the solution composition and temperature showed that in the range 25--40 degrees C in different solutions the excitation effects of BLM from general lipids of brain and a lecithin-cholesterol mixture are qualitatively similar and resemble those due to some biologically active substances diminishing the mechanical stability of BLM. Some possible mechanisms of excitation of BLM exposed to stress factors are discussed.