Effect of tetrapeptide A10, an agonist of μ-opioid receptors, on DNA synthesis in the myocardium and liver of albino rats in early postnatal ontogeny

The DNA synthesis in the myocardium and liver of 5–7-day-old albino rats after intraperitoneal injection of selective antagonist of μ-opioid receptors A10 (H-Tyr-D-Orn-Phe-Gly-OH) are studied using3H-thymidine autography. In the myocardium, both single (70 µg/kg) and 5-fold (100 µg/kg) administration of A10 significantly increases the intensity of labeling. The 5-fold administration of A10 induces an increase in abolute and relative mass of the heart. In the liver, the number of DNA-synthesizing hepatocytes rises in all experimental series. These data attest to a stimulating effect of μ-agonist on physiological regeneration of the myocardium and liver of albino rats in early postnatal ontogeny.