Recent work from this laboratory has provided information on the electrical behavior of mitochondrial membranes by applying patch clamp techniques. The macroscopic currents observed confirmed the presence of voltage sensitive channels in mitochondrial outer membranes previously observed after incorporation of an outer membrane protein (VDAC) into artificial bilayers. In addition, a novel behavior which may correspond to the transient formation of high conductance channels has been described. Completion of these studies and further attempts at obtaining single channel recordings with the outer membrane are proposed. Single channel behavior with the inner membrane has been observed in this laboratory using voltage clamp techniques. Multiple conductance levels are observed and a primary goal of this proposal is to characterize these levels in terms of their channel behavior, e.g. ion selectivity. The general macroscopic ionic currents associated with the initiation of metabolism include a) a decrease in resistance which is reversed by a metabolic inhibitor, b) a change in outward current, and c) a change in the magnitude of current fluctuations. Proposed work includes investigation of the underlying events responsible for these observations. In addition, the effect of imposed membrane potentials on ATP synthesis will be studied. Mitochondria are organelles within cells where biochemical reactions convert energy into a useful form that supports many other cell functions. The biochemical reactions going on in mitochondria have been the object of much research over many years. It is now generally believed that an important aspect of the regulation of mitochondrial function involves the distribution of ions across the mitochondrial membranes. "Patch clamp" techniques of electrophysiology that permit measurement of the permeability pathways for ions across the mitochondrial membrane have become available only relatively recently. The proposed research represents one of the first systematic studies of the permeability properties of intact mitochondrial membranes taking advantage of this technique. The results of this research will make an important contribution to basic knowledge of the function of these organelles.