title: Essential role of nitric oxide in sepsis-induced impairment of endothelium-derived hyperpolarizing factor-mediated relaxation in rat pulmonary artery.
abstract: Both endothelial nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) are important vasodilators in pulmonary circulation. Sepsis is known to impair endothelium-dependent dilation in the pulmonary vasculature, but the mechanisms are incompletely understood. We have examined the relative contribution of EDHF/NO to the attenuated endothelium-dependent relaxation of pulmonary artery in sepsis, and the role of inducible nitric oxide synthase (iNOS)-derived NO in this mechanism. Sepsis was induced in male adult Wistar rats by caecal ligation and puncture. At 18h after surgery, left and right branches of pulmonary arteries were isolated for tension recording, NO/cyclic guanosine monophosphate (cGMP) measurements, mRNA and protein expressions. Despite a marked decrease in the arterial endothelial nitric oxide synthase (eNOS) mRNA and phosphorylated-eNOS (p-eNOS) protein expressions in sepsis, endothelium-dependent relaxation to acetylcholine (ACh) mediated by NO, acetylcholine-stimulated NO release and tissue cGMP levels were moderately inhibited. Sepsis however abolished the N(G)-Nitro-l-arginine methyl ester (L-NAME)/indomethacin-resistant arterial relaxation (EDHF response) to acetylcholine in this vessel. In vitro treatment of the arterial rings from septic rats with 1400W, a selective inhibitor of iNOS restored the EDHF response, but had no effect on the acetylcholine-induced relaxation mediated by endothelial NO. The functional role of iNOS-derived NO in impairing EDHF-mediated relaxation was coincident with an increased basal NO production, iNOS mRNA and protein expressions in the rat pulmonary artery. In conclusion, the loss of the EDHF response may be primarily responsible for the endothelial dysfunction in sepsis, and its restoration by a selective iNOS inhibitor may improve pulmonary vasodilation.
authors.affiliation: Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar-243 122 (U.P), India.
authors.forename: Jaganathan
authors.initials: J
authors.lastname: Subramani
authors.forename: Marie Dennis Marcus
authors.initials: MD
authors.lastname: Leo
authors.forename: Kandaswamy
authors.initials: K
authors.lastname: Kathirvel
authors.forename: Rathinam
authors.initials: R
authors.lastname: Arunadevi
authors.forename: Thakur Uttam
authors.initials: TU
authors.lastname: Singh
authors.forename: Vellanki Ravi
authors.initials: VR
authors.lastname: Prakash
authors.forename: Santosh Kumar
authors.initials: SK
authors.lastname: Mishra
mesh_terms: D000818:Animals; D001685:Biological Factors / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D045462:Endothelium-Dependent Relaxing Factors / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D018805:Sepsis / Q000209:etiology*
chemical_list: D001685:Biological Factors; D045462:Endothelium-Dependent Relaxing Factors; C067410:endothelium-dependent hyperpolarization factor; D009569:Nitric Oxide