In vivo assessment of microvascular nitric oxide production and its relation with blood flow

Abstract

To assess the hypothesis that microvascular nitric oxide (NO) is critical to maintain blood flow and solute exchange, we quantified NO production in the hamster cheek pouch in vivo, correlating it with vascular dynamics. Hamsters (100-120 g) were anesthetized and prepared for measurement of microvessel diameters by intravital microscopy, of plasma flow by isotopic sodium clearance, and of NO production by chemiluminescence. Analysis of endothelial NO synthase (eNOS) location by immunocytochemistry and subcellular fractionation revealed that eNOS was present in arterioles and venules and was 67 +/- 7% membrane bound. Basal NO release was 60.1 +/- 5.1 pM/min (n = 35), and plasma flow was 2.95 +/- 0.27 microl/min (n = 29). Local NO synthase inhibition with 30 microM N(omega)-nitro-L-arginine reduced NO production to 8.6 +/- 2.6 pmol/min (-83 +/- 5%, n = 9) and plasma flow to 1.95 +/- 0.15 microl/min (-28 +/- 12%, n = 17) within 30-45 min, in parallel with constriction of arterioles (9-14%) and venules (19-25%). The effects of N(omega)-nitro-L-arginine (10-30 microM) were proportional to basal microvascular conductance (r = 0.7, P < 0.05) and fully prevented by 1 mM L-arginine. We conclude that in this tissue, NO production contributes to 35-50% of resting microvascular conductance and plasma-tissue exchange.

Coordinated Endothelial Nitric Oxide Synthase Activation by Translocation and Phosphorylation Determines Flow-Induced Nitric Oxide Production in Resistance Vessels

“…By combining analysis of eNOS band intensities (n=5) and the total protein content of each fraction (4,020±190 µg cytosolic, 530±17 µg microsomal, 450±70 µg Golgi, n=17), we estimated that in mesenteries perfused at 2 mL/min, approximately 50% of total mesentery eNOS was membrane bound, and distributed 3:2 between the microsomal and Golgi fractions. This proportion of eNOS associated to membrane is similar to that found in rat lungs by immunolocalization [8] and slightly smaller than that reported in the hamster cheek pouch in vivo [25]. In cultured endothelial cells, it has been extensively reported that the eNOS content associated to membrane reaches 90–100 % of total eNOS [3, 6, 11–13, 48].…”

Recombinant human erythropoietin improves angiogenesis and wound healing in experimental burn wounds*

“…Moreover, NO plays an important role in regulation of burn edema and in maintaining adequate perfusion in the burn area (31). The mechanism of action of NO could involve inhibition of smooth muscle tone in precapillary resistance vessels (32), inhibition of platelet adhesion and aggregation (33,34), or inhibition of polymorphonuclear granulocyte adhesion to the endothelial surface (35,36). The latter effect interferes with the ability of polymorphonuclear granulocytes to migrate into the damaged tissue and triggers the release of a wide variety of mediators (37,38), playing a central role in the circulatory and inflammationinduced changes that take place in the burned skin.…”

Molecular cloning and expression pattern of oriental river prawn (Macrobrachium nipponense) nitric oxide synthase

“…Consequently, it is crucial to the physiological functioning of NO. Many studies have confirmed that NOS has beneficial and versatile roles in the microvascular, neural, and immune systems (Figueroa et al, 2001). NOS sequences have been examined in several crustaceans (Rodríguez-Ramos et al, 2010;Yao et al, 2010;McDonald et al, 2011), but that of M. nipponense remains unknown.…”