[The role of sodium-proton exchange in the regulation of the electric and contractile activity of smooth muscles].

The Na+/H+-exchange inhibitor aethylisopropylamyloride was found to enhance the membrane resistance, the AP duration, and the duration of the guinea pig ureter's smooth muscle contraction. Tetraethylammonium and incubation in the Ca-free EG-TA-containing solution eliminated the activating effect of this inhibitor. Gramycidin A shortens the AP plateau. The Na+/H+-exchange mechanism seems to act under normal conditions. Alterations occurring in electrical and contractile activities of smooth muscle under the effect of the Na+/H+-exchange seem to result from the changes in the membrane Ca-dependent potassium conductivity.