RADIATION-INDUCED AND FREE RADICAL-MEDIATED INACTIVATION OF ION CHANNELS FORMED BY THE POLYENE ANTIBIOTIC AMPHOTERICIN-B IN LIPID-MEMBRANES- EFFECT OF RADICAL SCAVENGERS AND SINGLE-CHANNEL ANALYSIS

This paper is part of a study on the effect of ionizing radiation on i on channels in biological membranes. Ion channels formed by polyene an tibiotics amphotericin B or nystatin represent clusters of conjugated double bonds. As a consequence of this structural peculiarity, the con ductance of lipid membranes-in the presence of polyene channels-has be en found to decrease by several orders of magnitude at comparatively s mall doses of ionizing radiation. The phenomenon shows an inverse dose -rate behaviour similar to that of radiation-induced lipid peroxidatio n. We report on experiments pel formed in the presence of various radi cal scavengers, at varying cholesterol concentrations, and with differ ent lipids. They support the view that channel inactivation is due to free radical-induced peroxidation of the polyenes leading to a destabi lization of the barrel-like structure of the ion channels. Radiation-i nduced channel closing is shown for the first time at the level of sin gle-ion channels.