The heart is a major locus for the deleterious effects of chronic alcoholism and cardiac dysfunction can also be caused by acute ethanol ingestion. Previous studies have shown that ethanol depresses contractility in cardiac muscle and we have recently provided evidence that this can be accounted for, in part, by effects of ethanol on the cytosolic Ca2+ transients which mediate excitation-contraction coupling (E-C coupling) in heart muscle. there is also evidence that ethanol may affect the contractile apparatus of the cell directly. The objective of the present proposal is to elucidate the mechanism underlying the effects of ethanol on E-C coupling in isolated cardiac ventricular myocytes and to investigate the nature and mechanism of the Ca2+-independent effects of ethanol on contractility. this work will also include studies of the effects of ethanol on the responses of the cardiac myocytes to catecholamines. In addition, the alterations in E-C coupling in myocytes isolated from the hearts of animals following long term ethanol feeding will be investigated, using a recently described rat model of chronic alcoholism that mimics a number of the changes observed in alcoholic cardiomyopathy in humans. A further area of research of potential clinical importance is the interaction of acute ethanol ingestion with the cardiac effects of cocaine. We have shown that the latter drug also has direct inhibitory effects on E-C coupling in isolated cardiac myocytes, and therefore, the effects of combinations of these two agents on this process will be examined. The primary experimental approaches will involve the use of fluorescent Ca2+ indicators and a high-speed digital imaging system to follow Ca2+ fluxes in electrically-stimulated myocytes at the single cell level. This technique allows us to measure the kinetic parameters and subcellular distribution of cytosolic Ca+ transients with millisecond time resolution, while simultaneously monitoring cell contraction. We will also use the whole-cell configuration of patch-clamp to study the effects of ethanol on individual sarcolemmal ion conductances under voltage-clamp. The voltage-clamp and Ca2+ imaging methods will be combined to investigate how the effects of ethanol on ion channels might play a role in the inhibitory effect of ethanol on the Ca2+ transient. The long term objective of the study is to understand the basic mechanisms which underlie the cardiodepressant and toxic actions of acute and chronic ethanol ingestion and to determine how each of these mechanisms contributes to the harmful effects of ethanol in vivo.
