title: Acute hypoxia elevates nitric oxide generation in rat carotid body in vitro.
abstract: In acute hypoxia, the release of nitric oxide (NO) produced in rat carotid body is unclear. The concentration of NO was measured electrochemically with a Pt/Nafion/Pd-IrOx/POAP-modified electrode placed on the surface of isolated carotid bodies superfused with bicarbonate-buffer saline at 35 degrees C. In hypoxia, the concentration of NO in the carotid body was increased by 17+/-2 nM. The amount of NO release during hypoxia was augmented by increasing the number of carotid bodies surrounding the electrode and also in the presence of L-arginine. In addition, the hypoxia-induced elevation of NO was abolished by pretreatment with a nitric oxide synthase (NOS) inhibitor, L-N(G)-nitroarginine methylester (L-NAME). The results suggest that endogenous NO production in the carotid body increases during hypoxia. Electrophysiological measurement of single fiber activity in the sinus nerve revealed that L-NAME treatment enhances the afferent discharge in response to hypoxia. This confirms that the hypoxia-induced elevation of NO suppresses the carotid chemoreceptor response to hypoxia. Taken together, it is concluded that acute hypoxia increases NO generation in the rat carotid body, and that the elevated levels of NO suppress carotid chemoreceptor activity during hypoxia. Hence, NO may play an active inhibitory role in the control of carotid chemoreceptor activity during hypoxia.
authors.affiliation: Department of Medicine, University of Hong Kong, Pokfulam.
authors.forename: M L
authors.initials: ML
authors.lastname: Fung
authors.forename: J S
authors.initials: JS
authors.lastname: Ye
authors.forename: P C
authors.initials: PC
authors.lastname: Fung
mesh_terms: D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002344:Carotid Body / Q000378:metabolism*; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology; D004566:Electrodes; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000860:Hypoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester