A comparative investigation into the effect of chronic alcohol feeding on the myocardium of normotensive and hypertensive rats: An electrophoretic and biochemical study

We investigated whether the imposition of chronic alcohol in hypertension l eads to greater biochemical and cellular abnormalities of the myocardium th an those arising in normotension. Fifteen-week-old spontaneously hypertensi ve rats (SHR) and Wistar Kyoto (WKY) rats were fed ethanol-containing diets for six weeks. Particular attention was focused on the composition of cont ractile proteins identified by sodium dodecyl sulfate-polyacrylamide gel el ectrophoresis (SDS-PAGE), fractional rate of protein synthesis, and synthes is rates relative to RNA (RNA activity) or DNA (cellular efficiency). In ad dition, myocardial enzymes and adenine nucleotides were measured. In both S HR and WKY rats chronic ethanol caused a general decrease in the contents o f all nine contractile proteins with myosin heavy chain predominantly affec ted. Fractional rates of mixed (i.e., total) and myofibrillary proteins rem ained unaltered in both WKY rats and SHR, as were cellular efficiencies. Th e RNA activity was significantly reduced in ethanol-treated SHR but not in WKY rats. In ethanol-treated SHR, cardiac creatine kinase (CK) and malate d ehydrogenase (MDH) activities were increased, AMP levels were elevated, whi lst ATP levels and the energy charge were reduced. In WKY rats, the only si gnificant change related to increased aspartate aminotransferase activities in response to alcohol feeding. Although there were only subtle difference s between the response of the normotensive and hypertensive rats due to eth anol dosage, the reduced ATP levels and increased CK and MDH activities in SHR may reflect a greater susceptibility to ischaemic damage. Reduced contr actile protein content, particularly myosin heavy chain, may contribute to contractile defects, a common feature of subclinical and clinical alcoholic cardiomyopathy.