Nitric Oxide Synthase Inhibition Prevents Intestinal Damage in Gastroschisis: A Morphological Evaluation in Chick Embryos By Alaeddin Dilsiz, Ahmet H. GiindoQan, Murat Aktan, SelGuk Duman, and Tanju AktuQ izmir, Turkey Purpose: Increased small bowel nitric oxide (NO) synthase activity accused for postnatal intestinal dysmotility in gastros- chisis. The purpose of this study is to evaluate the effect of prenatal NO synthase inhibition on intestinal damage in gastroschisis. Methods: Sixteen-day-old fertilized chick eggs were divided into 4 groups. In the control group, the allantoic and amniotic membranes were opened to create a common cavity. In the gastroschisis group, a defect in the abdominal wall was made, and intestinal loops were exteriorized. In the gastros- chisis pretreated with L-NAME group, gastroschisis was created, and L-NAME was administered into the amnioallan- toic cavity for 4 days. In the gastroschisis sham pretreated group, after the same surgical procedure as the previous group, same amount of saline was given beside L-NAME. At the end of 20th day of incubation, intestinal morphological changes were investigated macroscopically and microscopi- cally. Results: Macroscopic changes such as shortening, thicken- ing, and fibrous adhesions were found in the exteriorized bowels of the just gastroschisis group and the gastroschisis pretreated saline group. However, there was only mild thick- ening in the gastroschisis pretreated with L-NAME group. Microscopically, compared with the gastroschisis group, serosal thickness, muscular thickness, and bowel wall thick- ness were found to be significantly lower in the gastroschisis pretreated with L-NAME group (128.0 t 19.3 pm and 239.5 2 3.0 pm ~57.0 -C 8.2 pm and 145.0 i 9.7 vm). Conclusion: It is possible to decrease intrauterine intestinal morphological changes in gastroschisis by inhibiting NO synthase. J Pediatr Surg 34:1248-1252. Copyright o 1999 by W.B. Saunders Company. INDEX WORDS: Gastroschisis, intestinal dysfunction, nitric oxide synthase. T HE USUAL clinical finding of gastroschisis includes shortening, thickening, matting, and adhesion of protruding intestine. These morphological changes are caused by either direct exposure to amniotic fluid or ischemia and lymphatic congestion caused by abdominal wall compression of the eviscerated intestines. In a recent study, Bealer et al’ have shown that gastroschisis increases small bowel nitric oxide (NO) synthase activity. They also have suggested that the increased NO synthase activity may contribute to the common clinical sequels such as dysmotility and malab- sorption. They have concluded that the increased NO synthase activity was secondary to intestinal damage (ID). We have carried out this study to investigate whether the increased NO synthase activity is just a result of ID seen in gastroschisis or an important step on the fetal pathway of ID. For this purpose, we investigated the effect of NO synthase inhibition on intestine in gastroschi- sis before birth. NG-nitro-L-arginine methyl ester (L- From the Departments of Pediatric Surgery and Histology- Embryology, Medical Faculty of Selcuk University, Konya, Turkey, and the Department of Pediatric Surgery, Medical Faculty of Dokuz Eyltil University, tmir, Turkey. Address reprint requests to Dr Alaeddin Dilsiz, Se&k Gniversitesi i”~p Fakiiltesi, (Zocuk Cerrahisi Anabilim Dab, 42080 Konya, Turkey. Copyright o 1999 by WE. Saunders Company 0022-3468/99/3408-0012$03.00/O 1248 NAME) was used as the inhibitor of NO synthase.2.3The investigation was based on histopathologic evaluation of the bowel wall in the chick embryo model of gastroschi- sis. MATERIALS AND METHODS Fifteen-day-old fertilized chick eggs were incubated at 37.5”C m 80% humidity. The eggs were divided into four groups of 30 eggs each. In the first group (control), through an eggshell window. the allantoic and amniotic membranes were opened to create a common cavity that resembles the amniotic cavity in humans. In the second group Cjust gastroschisis), after the embryos reached as in the control group, a defect (at least 1 cm in diameter) on the abdominal wall near the umb&al stalk was made, and intestinal loops were exteriorized our of abdomen. In the third group (gastroschisis pretreated with L-NAME), gastroschisis was created as in the gastroschisis group, and L-NAME was admimstered into the amnioallantoic cavity (AAC) at a daily dose of 20 pg per gram eggZs3 and continued for 4 days. In the fourth group (gastroschisis pretreated with saline). gastroschisis was created as in previous groups, and the same amount of saline as L-NAME was administered into AAC as in the third group. Surgical procedures were performed on the 16th day, using pre- viously published methods.4-6 In the gastroschisis pretreated with L-NAME group, L-NAME was injected in 0.05 mL of sterile 0.7% NaCl solution, which 1s lsotomc for chicks,’ whereas the fourth group received an injection of just 0.05 mL of 0.7% NaCl solution. After the procedures, the eggs were sealed with sterile dressing and incubated at the same conditions. At the end of 20th day, before hatching, the eggs were weighed and reopened. Dead embryos were discharged. Live embryos were exteriorized and weighed to calculate the chick to egg ratio as an indicator of embryonic development.d.7-9 Journal ofPediatric Surgery, Vol34, No 8 (August), 1999: pp 1248-1252