The proposed study will use synchronously contracting monolayer cultures of neonatal rat myocardial cells to investigate the effects of ethanol and acetaldehyde at a cellular level. The hypothesis to be tested is that ethanol and acetaldehyde could effect changes in active and passive membrane ion exchange by direct and possibly indirect, effects on sarcolemmal function, and that such changes could influence the inotropic and chronotropic state of the myocardium. The study proposes a detailed examination of the effect of ethanol (10 mg/dl-1000 mg/dl; 2 mM- 0.2M) and acetaldehyde (0.1 MU-0.1 mM) on cation exchange when applied to the cells, alone and in combination, both acutely and for periods of time up to several days. Using radioisotope tracer techniques, the time- and dose-dependent effects of the compounds on the Na, K and Ca content of the cells will be studied. Unidirectional active and passive Na, K and Ca influxes will be measured with particular attention being paid to specific parameters of membrane ion exchange, Na pump function, slow channel activity and Na:Ca exchange. The effects of ethanol and acetaldehyde on cyclic nucleotide content and adenylate changes in these parameters with changes in ion transport. Since ethanol is known to depress cardiac contractility additional studies will be carried out to examine the possible interactions between ethanol and commonly used positive inotropic drugs, ouabain and l- isoproterenol. As part of the studies of chronic ethanol treatment, myocyte cultures will be prepared from rats whose mothers have been given a high ethanol diet throughout gestation. Studies of membrane ion exchange will be carried out in these cells, in the continued presence of ethanol and in its absence, and compared to that in cultures prepared from control animals. This will further define the effects of chronic ethanol treatment and will also address the issue of possible changes in sarcolemmal function in the fetal alcohol syndrome. All of the preceding studies will be accompanied by parallel studies of the contractile behavior of the cells, as measured by a photo-optical recording system. Changes in ion exchange, cyclic nucleotide content and adenylate cyclase activity will be correlated with changes in contractile activity, with a principal focus on those aspects which have most bearing on myocardial performance. The study will thus attempt to define some of the sarcolemmal mechanisms involved in the cardiac effects of ethanol and acetaldehyde.
