45] Dynamic aspects of nitric oxide metabolism in the circulation and tissues

Abstract

Publisher Summary This chapter discusses the dynamic aspects of nitric oxide (NO) metabolism in the circulation and tissues. NO is an unstable gas with a free radical nature and is synthesized from arginine by NO synthase in various cells, such as endothelial cells, neurons, and hepatosplenic cells. NO forms dissociable complexes with various thiols and iron-containing proteins, such as guanylate cyclase and hemoglobin (Hb), thereby regulating vascular resistance, platelet aggregation, neurotransmission, and diverse functions of tissues. Because the half-life of NO is extremely short, particularly under aerobic conditions, in practice it is difficult to determine the in vivo generation and dynamic aspects of NO. To determine the generation of NO in vivo , various spin-trapping agents such as PTIO are used. NO forms dissociable complexes with thiols and iron-containing proteins. The paramagnetic nature of the nitrosylhemoglobin adduct (NO–Hb), is determined by electron spin resonance (ESR). The efficient mechanism by which circulating erythrocytes capture NO play a critical role in restricting the functions of the second messenger only at or near the site of generation.