title: Suppression of myocardial protein degradation in the rat during fasting. Effects of insulin, glucose, and leucine.
abstract: To study the effects of leucine, glucose, and insulin on myocardial protein degradation in fed and fasted nutritional states, we developed and validated a sensitive method for measuring rates of total protein degradation in rat isolated left atrial preparations. Fasting resulted in a progressive decrease in myocardial protein breakdown to 71% of control over a 24-hour period, with no further reduction in degradation rate between 24 and 72 hours of fasting. Insulin (100 mU/ml) suppressed atrial protein degradation by 38% in fed animals (P less than 0.001) and by 51% in fasted animals (P less than 0.001). Glucose alone had no effect on protein degradation in either nutritional state. At 5 times normal plasma levels, leucine suppressed protein breakdown by 21% in fed and by 15% in fasted animals. The decrease in degradation induced by fasting and the absence of an effect of glucose are in contrast to the behavior reported for skeletal muscle.
mesh_terms: D000255:Adenosine Triphosphate; D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D005215:Fasting; D005947:Glucose / Q000494:pharmacology; D006325:Heart Atria / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D007930:Leucine / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D014443:Tyrosine / Q000096:biosynthesis / Q000378:metabolism
chemical_list: D007328:Insulin; D011506:Proteins; D014443:Tyrosine; D000255:Adenosine Triphosphate; D003513:Cycloheximide; D007930:Leucine; D005947:Glucose