Reduced Messenger RNA Expression of the Neuronal Nitric Oxide Synthase Gene in Infantile Hypertrophic Pyloric Stenosis

Hur, Min Hee; Seo, Jeong Meen; Cho, Eung Ho; Yi, Hyeon Gyu; Park, Chang Shin; Cha, Young Nam; Hong, Kee Chun; Woo, Ze Hong

Abstract

PURPOSE: Nitric oxide synthesized by neuronal nitric oxide synthase (nNOS) has been described as a mediator of smooth muscle relaxation in the mammalian gastrointestinal tract. Impaired expression of the nNOS gene is suggested in the development of infantile hypertrophic pyloric stenosis (IHPS). We examined the expression of nNOS mRNA in pyloric muscle biopsy specimens obtained from 8 patients with IHPS and attempted to correlate the results with the clinical characteristics. METHODS: The expression of nNOS mRNA in pyloric muscle biopsy specimens for 8 patients with IHPS was examined using a reverse transcription- polymerase chain reaction (RT-PCR) technique. For the control, a smooth muscle layer specimen of a neonate with a normal pylorus was used. RESULTS: In the control specimen, the level of nNOS mRNA expression was 48.4% of beta-actin mRNA. In the two thinnest (each 3 mm) of pyloric muscle thicknesses as determined by ultra-sonography, the expressed nNOS mRNA were 16.7% and 30.3%. The two thickest (each 8.3 mm) expressed as 35.3% and 22.9% nNOS. The two samples from the earliest age of symptomatic onset (1 day, 7 days after birth) expressed as 25.6% and 4.8%. The two from the latest age of onset (each 30 days) expressed as 7.4% and 10.5%. The control specimen revealed a higher level of nNOS mRNA expression than those of the IHPS specimens. There was no significant correlation between the clinical characteristics and the levels of nNOS mRNA in the IHPS specimens. CONCLUSION: Since a low level of nNOS mRNA expression may lead to impaired production of NO, our observations indicate that the hypertrophic pyloric muscle of an IHPS patient may be the result of a reduced expression of the nNOS gene at the mRNA level. In IHPS patients, there was no correlation between the clinical characteristics and the levels of expressed nNOS mRNA.