Modulation of NO bioavailability by temporal variability of cell‐free layer width in the arterioles

Abstract

The formation of a cell (erythrocyte)‐free layer near the vessel wall during blood flow is capable of attenuating NO consumption by the red blood cells and thus improves the preservation of NO in the smooth muscle for eliciting vasodilatory responses. This study utilized a transient NO transport mathematical model to predict how temporal variability exhibited by the layer width and its relevant transient physiological responses could modulate NO preservation by this diffusion barrier at high pseudoshear rates (291.5 ± 13.5 s−1). Data on cell‐free layer width was experimentally acquired from arterioles (48.4 ± 2.3 μm) of the rat cremaster muscle. We found that a time‐varying diffusion barrier could lead to a slight decrease (2% – 6%) in NO bioavailability and this effect was independent of transient changes in NO scavenging rate in the blood lumen. Conversely, transient changes in wall shear stress and accompanying NO release rate played a dominant role in reversing this decline such that an augmentation in NO bioavailability of between 3% – 15% was found. However this increase was not sufficient to induce any significant change in vascular tone. This study highlighted the importance of accounting for transient wall shear stress effect on NO release rate as mediated by the layer width temporal variability when assessing the physiological implication of the layer on NO bioavailability in arterioles.