ALCOHOL STIMULATES NA+/CA2+ EXCHANGE IN BRAIN MITOCHONDRIA

Ethanol, at low concentrations, specifically stimulates the Na+-dependent Ca2+-efflux in brain mitochondria. In addition, at higher concentrations, ethanol inhibits the Na+-independent Ca2+-efflux. The electrogenic Ca2+-uptake system is not affected by ethanol. The specific stimulation of Na+/Ca2+ exchange reaches a maximum of 60% stimulation, with half-maximal stimulation at 130 mM ethanol. The inhibition of the Na+-independent efflux is proportional to the ethanol concentration, becoming significant only above 200 mM, with 50% inhibition at 0.5 M. The inhibition of the Na+-independent efflux is, in large part, due to an inhibition of the activation of the Cyclosporin-sensitive pore. Long-term ethanol-feeding had no effect on the Ca2+ transport systems and their sensitivity to acute ethanol treatment. It is suggested that the stimulation of the Na+-dependent Ca2+-efflux, which is the dominant Ca2+ efflux pathway in brain mitochondria, contributes to the intoxicating effects of ethanol.