Abstract

The significance of microvascular NO production in the regulation of blood flow and solute exchange in the hamster cheek pouch (HCP) has been estimated by pharmacological maneuvers, such as blockade of eNOS and/or admininstration of NO donors. However, in vivo direct measurements of NO production/release in this microcirculatory bed has not been reported. In this study, we determined NO production in the HCP prepared for intravital microscopy, by measuring NO and nitrite accumulation in the superfusate. Total NO and nitrite content in the superfusate was detected by the chemoluminiscence reaction with ozone after reduction in potassium iodine / acetic acid (Sievers NO Analyzer 280). In control conditions, basal NO release in the HCP was 69.6 ± 9.7 pmol/min (n=10). Superfusion with 30 uM L-Nitro-Arginine, reduced NO release to 20.1 ± 10.0 pmol/min after 1 hr treatment. The effect of L-Nitro-arginine was fully prevented by L-Arginine (1mM). The time course and magnitude of changes in NO - nitrite release were closely correlated with changes in microvessel diameters and blood flow, as determined by clearance of isotopic sodium and intravital observation. Measuring clearance of exogenous and endogenous nitrite allow us to estimate NO produced by local endothelium and the contribution of plasma nitrite, i.e., not-locally produced.