Chronic ethanol abuse is associated with a variety of cardiovascular disorders including stroke, heart failure, hypertension and sudden death. Congestive cardiomyopathy related to alcoholism has been reported as the single most frequently identifiable cause of cardiomyopathy. At present, no clear explanation exists concerning the molecular mechanism responsible for cardiovascular dysfunction as a result of alcohol abuse. Recent work in our laboratory has shown that chronic ethanol treatment induces a differential cardiac expression of atrial natriuretic peptide genes. Atrial natriuretic peptide (ANP) was discovered and sequenced in the Principal Investigator's laboratory and recently a second atrial peptide called iso-rANP was also discovered by the PI. This peptide is highly homologous with ANP but is expressed by its own gene. In the present study we propose to continue our investigations with respect to the involvement of NAP and iso-rANP in cardiac dysfunction following ethanol ingestion. In preliminary studies we have already shown that acute ethanol ingestion alters the gene expression of A- and B-type (iso- rANP) and reduces the circulating plasma levels of ANP. We have further demonstrated that cultured cardiac myocytes can be used as a model to study the gene expression and release of atrial natriuretic peptides. Our proposed studies, therefore, involve examining the effect of ethanol on the expression, synthesis and release ANPs in animal and cell culture models. Specifically, in both chronic and acute alcoholic rats we will characterize the mRNA levels of ANP and iso-rANP in atria and ventricles, measure atrial ventricular and plasma levels of ANP and iso-rANP in conjunction with measurement of arterial blood pressure and heart rate. The effects of the ethanol on the signal transduction will be examined. We will examine the receptor binding of ANP and iso-rANP, the induction of cyclic GMP and the phosphorylation of proteins in the cell as a result of the action of ANP and the modulation, if any, of ethanol on these parameters. We will also determine the control of the regulation of natriuretic peptide synthesis and release focussing attention on the mechanism of alteration of plasma levels of atrial peptides and on the effect of hypotensive agents on ANP and iso-rANP gene expression and release. These studies should enhance our understanding of the role of cardiac hormones in cardiac dysfunction due to ethanol intoxication.
