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Nitric oxide targets in the guinea-pig intestine identified by induction of cyclic GMP immunoreactivity
H M Young1, K McConalogue, J B Furness
1Department of Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria, Australia.
Abstract:
The immunohistochemical localization of cyclic GMP was used to determine potential physiological sites of action of nitric oxide in the guinea-pig small intestine and colon. In control tissue, cyclic GMP-immunoreactivity was observed only in macrophages, whose identity was confirmed by double-label experiments using either F4/80, a macrophage-specific antibody, or fluorescein isothiocyanate-labelled dextran injected intravenously. Following exposure to the nitric oxide donor, sodium nitroprusside, cyclic GMP-immunoreactivity was induced in subpopulations of neurons in the myenteric and submucosal plexuses of the ileum and colon. In the colon, cyclic GMP-immunoreactivity was induced in 5-10% of myenteric neurons. The cyclic GMP-immunoreactive neurons did not contain nitric oxide synthase. In the ileum, cyclic GMP-immunoreactive neurons comprised about 2% of myenteric neurons and 40% of submucosal neurons; these cyclic GMP-immunoreactive neurons were also immunoreactive for vasoactive intestinal peptide, but they did not contain nitric oxide synthase. Interstitial cells between the mesothelium and the longitudinal muscle layer, vascular smooth muscle and vascular pericytes also showed sodium nitroprusside-induced cyclic GMP-immunoreactivity. The interstitial cells of Cajal at the inner surface of the circular muscle layer and the smooth muscle cells of the circular and longitudinal muscle layers showed increases in cyclic GMP-immunoreactivity that varied in extent from animal to animal. The results suggest that nitric oxide could act at several sites in the intestine through the stimulation of guanylyl cyclase.
Insights
Nitric oxide (NO) activates guanylyl cyclase, increasing cyclic GMP (cGMP) in guinea-pig intestine. NO donors induced cGMP in neurons and other cells, suggesting diverse physiological roles for NO signaling in the gut.
Area of Science:
- Gastroenterology
- Neuroscience
- Cellular Biology
Background:
- Nitric oxide (NO) is a key signaling molecule in the gastrointestinal tract.
- Understanding the precise cellular targets and physiological actions of NO is crucial for comprehending gut function.
Purpose of the Study:
- To investigate the cellular localization of cyclic GMP (cGMP) in response to nitric oxide stimulation in the guinea-pig small intestine and colon.
- To identify potential physiological sites of action for nitric oxide within the enteric nervous system and other intestinal tissues.
Main Methods:
- Immunohistochemistry was employed to detect cyclic GMP (cGMP) localization.
- The nitric oxide donor, sodium nitroprusside, was used to induce cGMP.
- Double-labeling experiments confirmed macrophage identity and characterized neuronal populations.
Main Results:
- Sodium nitroprusside induced cGMP-immunoreactivity in subpopulations of myenteric and submucosal neurons in the ileum and colon.
- Specific neuronal populations, including vasoactive intestinal peptide (VIP)-expressing neurons in the ileum, showed increased cGMP.
- cGMP induction was also observed in interstitial cells, vascular cells, and smooth muscle cells, with varying intensity.
Conclusions:
- Nitric oxide (NO) acts on multiple cell types within the guinea-pig intestine, including neurons and smooth muscle.
- The stimulation of guanylyl cyclase by NO likely mediates diverse physiological responses in the gut.
- These findings highlight the broad signaling capacity of NO in regulating intestinal function.