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.

Prolonged feeding of ethanol to the young growing guinea pig. II. A model to study the effects of severe ischemia on cardiac protein synthesis.

Although acute perfusion of guinea pig hearts with ethanol does not affect cardiac protein synthesis, the latter is inhibited after prolonged ingestion of ethanol when tested in an in vitro system with the working right ventricle. This study reports on the added stress of ischemia on such hearts. Hearts were removed from maturing guinea pigs after 13-16 weeks of ingesting 10% ethanol and were perfused in vitro under conditions of relative ischemia (one-sixth of normal coronary flow) with maintenance of right ventricular load and outflow resistance identical to normal pre-ischemic levels.

Prolonged feeding of ethanol to the young growing guinea pig: 1. The effect on protein synthesis in the afterloaded right ventricle measured in vitro.

Newly weaned guinea pigs weighing approximately 300 g were fed normal laboratory diets with drinking water containing 5.5% ethanol as the sole source of liquid for periods of 8-11 weeks. Growth was continuous with this diet.

Effect of hydrostatic pressure on isolated cardiac nuclei: Stimulation of RNA polymerase II activity.

RNA polymerase activity was measured in isolated cardiac nuclei subjected to hydrostatic pressure. After 20 min of pressure, Mn2+ stimulated RNA polymerase II activity was increased. The response to pressure was inhibited by low concentrations of alpha-amanitin (1.

The effect of pressure or flow stress on right ventricular protein synthesis in the face of constant and restricted coronary perfusion.

Cardiac stress produced by hypertension or excess volume loading results in different types of hypertrophy. Elevated left ventricular pressure rapidly results in increased myocardial protein synthesis in vivo and in vitro, but such rapid alterations are not consistently seen in volume loading. The difference in response is difficult to clarify since it is not possible to effect alterations in left ventricular pressure or perfusion without profoundly affecting coronary perfusion.