[Change in the opioid peptide level in the heart and blood plasma during acute myocardia ischemia complicated by ventricular fibrillation].

After occlusion of the anterior descending coronary artery content of opioid peptides was increased 2-3-fold in blood plasma of all the rats with and without ventricular fibrillation. Content of Leu-enkephalin was decreased in ischemic and non-ischemic regions of myocardium under conditions of ventricular fibrillation. At the same time, concentration of Met-enkephalin in myocardium was increased in the acute ischemia independently on the effect of fibrillation. Synthetic enzyme-resistant derivative of Leu-enkephalin, administered before acute myocardial ischemia, prevented a decrease in the ventricular fibrillation threshold caused by the occlusion. Alteration of the Leu-enkephalin content in heart tissue appears to be importance in pathogenesis of ventricular fibrillation developed after acute myocardial ischemia.