Altered mRNA expression of the neuronal nitric oxide synthase gene in Hirschsprung's disease

Nitric oxide has been described as an inhibitory neurotransmitter to mediate smooth muscle relaxation in the mammalian gastrointestinal tract. The enzyme neuronal nitric oxide synthase (NOS) catalyzes the formation of NO. The authors examined the expression of neuronal NOS gene at the mRNA level in intestinal specimens from seven patients who had Hirschsprung's disease (HD) using reverse transcription polymerase chain reaction (RT-PCR) technique. With 35 cycles of PCR reaction, substantial signals of neuronal NOS mRNA were observed in the ganglionic bowel in all seven patients, whereas in the aganglionic bowel, neuronal NOS signals were weak in three patients, and undetectable in four patients. By increasing the PCR cycle to 40 cycles, barely detectable signals were observed in two of the latter four patients. Semiquantitative analysis in the three patients who showed weak signals with 35 cycles of PCR indicated that neuronal NOS mRNA expression in aganglionic bowel was decreased at least 1/50 to 1/100 of the level expressed in ganglionic bowel. Because absence or low level of expression of neuronal NOS mRNA may lead to impaired production of NO, our observations suggest that motility dysfunction in HD may be as a result of markedly decreased or no expression of the neuronal NOS gene at the mRNA level.