Expression of endothelial constitutive nitric oxide synthase mRNA in gastrointestinal mucosa and its downregulation by endotoxin.

Endothelial nitric oxide exerts local vasodilatory actions in the gastrointestinal (GI) microvasculature and is proposed to play a role in enteric vasomotor regulation. The aims of this study were to characterize the tissue distribution of mRNA for endothelial nitric oxide synthase (NOS-III) and to examine its response to endotoxin challenge in vivo. We demonstrate the expression of NOS-III mRNA and protein in mucosa throughout the gastrointestinal tract and show for the first time that NOS-III mRNA expression in the GI mucosa was down-regulated in the rats treated with endotoxin. The ubiquitous expression of NOS-III mRNA in digestive tissues is consistent with the proposed role of NOS-III in the physiology of the gastrointestinal tract. The decreased NOS-III mRNA, in parallel to induction of inducible NOS (NOS-II) mRNA, may contribute to the impaired endothelium-dependent relaxation and damaged mucosal integrity during sepsis.