[Effect of increased calcium ion concentration on the electrical and contractile activity of guinea pig ureter smooth muscle].

Experiments were performed on the smooth muscle cells of the guinea pig ureter by means of the double sucrose-gap method. An increase of Ca2+ concentration (22 mM/1) in Ringer-Locke solution causes hyperpolarization and a slight increase of the membrane resistance. The amplitude of the first spike potential and the plateau decreases, the amplitude of oscillations increases. In sodium-free Ringer-Locke solution when the action potential in the smooth muscle cells of the ureter turns into a simple spike potential, an increase of Ca2+ concentration causes a marked increase of the action potential amplitude.