Theoretical approach to description of time-dependent nitric oxide effects in the vasculature.

Nitric oxide (NO) is one of the most important signal compounds in a living cell. As a typical free radical it has both toxic and physiological effects and their balance is determined by a spatial distribution of NO concentration. Moreover, some biological functions, especially NO-mediated relaxation of blood vessels, have to be time-limited. In order to circumscribe this phenomenon non steady-state mathematical model has been used for description of nitric oxide diffusion in vascular smooth muscle. It was shown that the microvascular relaxation could be observed even after a short time of NO production in the endothelium. This time is up to 3 times below that needed to reach the steady-state spatial NO gradient. However, the effect of nitric oxide essentially depends on the rate of NO production and blood vessel diameter. Furthermore, non steady-state nitric oxide concentration gradient was represented as an analytical function of time and coordinate. It is essential that this function describes a common case of one-dimensional diffusion of uncharged low-mass molecules. Thus, the results can be used for calculation of an upper estimation of experimental data.