NADPH-diaphorase activity in piglet intestinal mucosa

The distribution of the enzyme synthesizing nitric oxide (NO) has been characterized in several mammalian enteric nervous systems. Two methods, immunohistochemical staining, employing anti-nitric oxide synthase antibodies, and histochemical localization of NADPH-diaphorase (NADPH-D), have given the same results. On the other hand, few studies have investigated nitric oxide synthase (NOS) in the gastrointestinal mucosa. Our study demonstrated the presence and distribution of the enzyme, NADPH-D, throughout all layers of the neonatal piglet intestinal tract. In the neonatal piglet, NADPH-D activity was found in nerve fibers parallel to the circular and to the longitudinal muscles and in the ganglion cells of Auerbach's plexus. However, the majority of NADPH-D activity was localized to the mucosa. Furthermore, the most intense activity in the mucosa was observed in villous epithelial cells. Other mucosal cells which were NADPH-D positive included the glandular epithelium and crypt cells. In addition, glandular epithelium in the deeper submucosa had very strong NADPH-D activity. Our results support the hypothesis that locally produced NO mediates physiological functions in the intestinal mucosa and submucosa.