Effect of mu-opiate receptor agonist tetrapeptide A10 on DNA synthesis and protein content in the myocardium of albino rats.

Effect of intraperitoneal injection of tetrapeptide A10 (H-Tyr-D-Orn-Phe-Gly-OH), selective mu-opiate receptor agonist, synthetic analog of dermorphine, in a dose of 100 microg/kg on DNA synthesis and protein content in the myocardium was studied in albino rats. Five injections of tetrapeptide on days 2-6 after birth caused no changes in DNA synthesis 17 days after the last injection, i. e. in 24-day rats. The number of nucleoli and their area increased. In adult males long-term (3-week) treatment with tetrapeptide A10 increased the number of nucleoli and the mean and integral optical density of isolated cardiomyocytes stained with amido black B, which probably attested to activation of protein synthesis in the myocardium. Simultaneously, the content of catecholamines in the heart increased. These data are comparable with delayed effects of kappa-opiate receptor agonist dinorphine A1-13 and indicate that morphogenetic properties of opioid peptides in rat myocardium are realized via the same routes.