Effects of agents that inactivate free radical NO (NO•) on nitroxyl anion‐mediated relaxations, and on the detection of NO• released from the nitroxyl anion donor Angeli's salt

• Published in: British journal of pharmacology 2001-10, Vol.134 (3), p.521-528
• Main Authors: Ellis, Anthie, Lu, Hong, Li, Chun Guang, Rand, Michael J
• Format: Article
• Language: English
• Subjects: Angeli's salt; Animals; anococcygeus muscle (rat); Antioxidants - pharmacology; aorta (rat); Aorta, Thoracic - drug effects; Aorta, Thoracic - metabolism; Benzoates - pharmacology; Biological and medical sciences; Blood vessels and receptors; carboxy‐PTIO; Free Radicals - antagonists & inhibitors; Free Radicals - metabolism; Fundamental and applied biological sciences. Psychology; Hematinics - pharmacology; hydroxocobalamin; Hydroxocobalamin - pharmacology; Imidazoles - pharmacology; In Vitro Techniques; Intestine. Mesentery; Male; Muscle Relaxation - drug effects; Muscle Relaxation - physiology; Muscle, Smooth - drug effects; Muscle, Smooth - metabolism; nitric oxide; Nitric Oxide - antagonists & inhibitors; Nitric Oxide - metabolism; Nitrites - pharmacology; Nitrogen Oxides - pharmacology; nitroxyl anions; NO sensor electrode; pyrogallol; Pyrogallol - pharmacology; Rats; Rats, Sprague-Dawley; Vertebrates: cardiovascular system; Vertebrates: digestive system
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0704287

The effects of agents that inactivate free radical nitric oxide (carboxy‐PTIO, hydroxocobalamin and pyrogallol) were tested on relaxations produced by the nitroxyl anion (NO−) donor Angeli's salt in rat aortic rings and anococcygeus muscles. The amount of NO• generated from Angeli's salt in the presence of these agents was measured using a NO•‐selective electrode sensor. Carboxy‐PTIO (100, 300 μM), hydroxocobalamin (30, 100 μM) and pyrogallol (10, 30 μM) significantly reduced relaxations produced by Angeli's salt (0.3 μM) in aortic rings but not in anococcygeus muscles. NO• generated from Angeli's salt (0.1 – 10 μM), as detected by the sensor electrode, was less than 0.5% of the amount of Angeli's salt added. Carboxy‐PTIO (100 μM) and hydroxocobalamin (30 μM), but not pyrogallol significantly increased the amount of NO• detected. In the presence of an oxidizing agent copper [II] (as CuSO4 100 μM), the amount of NO• detected from 0.3 μM of Angeli's salt increased from an undetectable level of 142.7±15.7 nM (equivalent to 47.6% of Angeli's salt added). Under these conditions, carboxy‐PTIO, hydroxocobalamin and pyrogallol significantly reduced the amount of NO• detected from Angeli's salt as well as the signal generated by an equivalent amount of authentic NO (0.33 μM). The difference in effects of these agents on relaxations to Angeli's salt in the aorta and the anococcygeus muscle may be explained by the ready conversion of NO− to NO• in the aorta through an unidentified mechanism, which makes NO− susceptible to inactivation by these agents. Furthermore, in addition to inactivating NO•, carboxy‐PTIO and hydroxocobalamin may themselves oxidize NO− to NO•, albeit slightly. British Journal of Pharmacology (2001) 134, 521–528; doi:10.1038/sj.bjp.0704287