[A kinetic model of stationary calcium metabolism in smooth muscle cells].

A model is proposed for Ca2+ stationary exchange in the myometrium cells in the absence of effects activating calcium channels of the plasmic membrane. The results of the model analysis point to an important role of the calcium pump (but not on Na(+)-Ca2+ exchanger) of the sarcolemma in providing the long-term regulation of physiologically significant concentration of ionized calcium in the smooth muscle cells. Ability of the calcium pump to efficiently compensate Ca2+ basal current continuously entering the myocytes at rest is proved. It is suggested that the stationary transsarcolemmal exchange of calcium (the system "basal calcium current--ATP-dependent transfer of Ca2+") underlies the control mechanism of the myometrium basal tonus, while a disturbance of the stationary state (with the pump inhibition) provides activation of the smooth muscle tonic contraction.