A computational model of nitric oxide production and transport in a parallel plate flow chamber

We developed a mathematical model to investigate the production and transport of nitric oxide (NO) generated by a monolayer of cultured endothelial cells exposed to flow in a parallel plate flow chamber. The objectives were to provide a theoretical framework for interpreting experimental observations and to suggest a quantitative relationship between shear stress and NO production rate. NO production was described as a combination of a basal production rate term and a shear-dependent term. Our results show that the shear stress-dependence of the production of NO by the endothelium influences the nature of mass transport within the boundary layer. We found that the steady state NO concentration near the endothelial surface exhibits a biphasic dependence on shear stress, in which at low flow, NO concentration decreases owing to the enhanced removal by convective transport while only at higher shear stresses does the increased production cause an increase in NO concentration. The unsteady response to step changes in flow exhibits transient fluctuations in NO that can be explained by time-dependent changes in the diffusive and convective mass transport as the concentration profile evolves. Our results indicate that this model can be used to determine the relationship between shear stress and NO production rate from measurements of NO concentration.