[The mechanisms in NO-dependent regulation of electrical and mechanical activity in smooth muscles]

The role of nitric oxide (NO) and its implication in intracellular and intercellular signaling pathways attract an attention of many research teams up to now. Away of its signaling functions. NO is considered as one of the key molecules in maintenance of balance between the physiological and pathological processes due to cytoprotective and cytotoxic functions of this molecule. In this regard, elucidation of the NO-dependent mechanisms, involved into the physiological processes and pathophysiological reactions, remains an urgent problem of conntemporary biology and medicine. Analysis of obtained results establishes a relative contribution of electro- and pharmaco-mechanical coupling mechanisms in NO-dependent regulation of smooth muscle cels (SMC) functions. The authors show that elevation of intracellular Ca2+ concentration by biologically active substances promotes relaxing effect of NO through both voltage-dependent and -independent intracellular mechanisms of calcium redistribution. Namely the peculiarities of considered mechanisms in each certain type of SMCs cause the final direction of alterations in contractility and membrane potential. It has been shown that voltage-dependent effects of NO are mediated by suppression of calcium and/or sodium components and modulation of Ca2+ -dependent and ATP-seisitive potassium components of SMC membrane permeability, Voltage-independent NO control of mechanical smooth muscles activity mainly is mediated by 1) modulation of protein kinase C (PK-C) branch of calcium signaling system, 2) ratio of cyclic nucleotides intracellular concentrations (cGMP/cAMP), and 3) directional mode of electrosilent Na+, K+, 2Cl- -cotransport. Our results show that the features of the myogenic effects of NO are caused by the peculiarities of PK-C operation in SMC.