Prolonged feeding of ethanol to the young growing guinea pig. III. Effect on the synthesis of the myocardial contractile proteins.

Prolonged ingestion of ethanol may lead to a cardiomyopathy, and studies in the experimental animal have demonstrated alterations in protein metabolism. These changes include depression of protein synthesis with acetaldehyde in the acute experiment, in vitro, and after chronic ethanol ingestion in vivo. The present studies were initiated to see if the inhibition of protein synthesis following prolonged ethanol ingestion involved myocardial contractile proteins. Newly weaned guinea pigs, weighing 350 g, were placed on a regimen of normal laboratory diet with 10% ethanol in the drinking water. Calorie-matched controls, drinking dextromaltose in the water, were simultaneously run. After 40 weeks of ingesting 10% ethanol in the drinking water, hearts from growing guinea pigs were removed and synthesis of myocardial contractile proteins (myosin heavy chains, light chains (LC1, LC2), actin, and tropomyosin) assayed in vitro with 3H-labeled amino acids. With aging, there was a decrease in the rates of synthesis of all the contractile proteins. After 40 weeks of ethanol ingestion, the synthetic rates of myosin heavy and light chains and tropomyosin were the same as in calorie-matched controls, but the synthetic rate of actin was significantly decreased by 20% (p less than 0.01). This decrease in actin synthesis may be the first indication of ultimate inhibition of synthesis of all the contractile proteins which may lead to myofibrillar disorganization and vacuolization reported after chronic ethanol ingestion.