THE EFFECT OF NITRIC OXIDE (NO) ON CIRCULAR SMOOTH MUSCLE OF PYLOR IN RAT EMBRYO

Nitric oxide (NO) is an unstable small molecule which acts as lipophilic free radicals. It is synthesized in different mammalian cells and thought to be involved in many physiological and pathological conditions. There are many evidences that show NO acts as a neurotransmitter in Non-Adrenergic, Non-Cholinergic (NANC) nerves, innervating smooth muscles of digestive system and also has direct influence on smooth muscle cells. Infantile hypertrophic pyloric stenosis(IHPS) is one of the most common pathological conditions among the neonates. It is thought that any failure in NO synthesis could be one of the reasons of IHPS. Pregnant Sprague-Dawley rats were used in this study. Different doses of the L-NAME (20-80mg/kg) as an NO inhibitor in normal saline was injected intraperitoneal (IP) during the last week of pregnancy period per day. The embryos were removed on the day of expected delivery. The stomach and duodenum were dissected, fixed by Bouin solution and tissue processing was done. By using rotatory microtome, 5μ serial cross sections were obtained and stained with Trichrom-Mason and Pop-Nicola. Statistical analysis of macroscopic and light microscopic findings showed that 80mg/kg of L-NAME causes significant changes in embryos of trial group including: IUGR, hind-limb disruption, embryo absorption, pyloric hypertrophy and hyperplasia. On the basis of these results it is believed that 80mg/kg of L-NAME can be one of the reasons of pyloric stenosis in infants.