[The role of sodium ions of the medium on the generation of spike activity in the ureter].

In sodium-free Krebs solution ureter cells are able to generate action potentials. Logarithm of time, during which spikes are generated, is in proportion to the concentration of calcium ions in the surrounding medium in interval from 2.5 to 15 mmol/l. The addition of 20 mmol/l Na+ ions into the external solution is able to reestablish prolonged electrical activity of ureter. In sodium-free solution it is possible the reestablishment of short duration activity which depends on K+ ions concentration in surroundings. It is supposed that intracellular concentration of calcium ions in ureter may be regulated with the help of Na+/Ca++ exchange mechanism.