[Urea synthesis in the myocardium].

Urea synthesis was studied in the isolated rat heart-perfused with ammonium chloride (10 mM), mixtures of ammonium chloride (10 mM) and 1-aspartic acid (10 mM), 1-ornithine (2.5 mM), 1-arginine (10mM), 1-glutamine (10 mM), 1-alanine (10 mM), 1-leucine (5 mM) and pyruvate (5mM). Ammonium chloride and 1-arginine are the most effective activators of urea synthesis, while 1-leucine and pyruvate produce an inhibitory action. The possibility of ammonia hinding in heart tissue was shown by means of (15)N. The amount of urea incorporated (15)N grows as the concentration of (15)N-ammonium in the perfusate increases from 1.6 to 3.4 mM. Isoproterenol-induced necrosis of the heart muscle leads to a significant increase in the urea incorporated (15)N.