Background and Aims: The interstitial cell (IC) network may be of fundamental importance in regulating gastrointestinal motility. Intestinal smooth muscle cells are depolarized in the absence of ICs, and there are no spontaneous slow waves. The messenger molecules between IC network and smooth muscle are unknown. Exogenous administration of CO relaxes the opossum internal anal sphincter and the guinea pig ileum, and it modulates potassium current and membrane potential of circular smooth muscle cells of the human jejunum. The aim of this study was to determine whether heme oxygenase (HO)- 1 and HO-2, enzymes that catalyze the production of CO, are present in the IC network of the mouse small intestine. Methods: Antibodies specific for c- Kit, HO-1, and HO-2 were used for immunohistochemistry. Confocal images were obtained and were volume rendered, and the images were converted into three- dimensional images. Results: HO-2-like but not HO-1-like immunoreactivity was found in IC networks associated with the myenteric plexus and the deep muscular plexus. Conclusions: HO-2 but not HO-1 is present in the IC cell network of the mouse small intestine. The enzymatic activity of HO-2 will result in the endogenous production of CO in IC networks of the mouse small intestine.
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