The aim of our study was to inve stigate mechanism of action of endothelins 1, 2 and 3 on spontaneous activity, tone and intraluminal pressure of human ureter. Both longitudinal tension and intraluminal pressure were recorded from the isolated segments of proximal human ureter. Endothelins 1, 2 and 3 (5.35x10 -11 M- 5.05x10-8M) produced concentration-dependent tonic contraction and sustained increase in intraluminal pressure of isolated preparations of hum an ureter. Endo thelins 1 and 3 produced also concentration-dependent inhibition of spontaneous, phasic contractions of the isolated preparations. Selective antagonist of ETA receptors BQ123 and selective antagonist of ET B receptors BQ788 produced significant inhibition of endothelin-1-induced tonic contraction (pA2=8.80 and 6.55, respectively) and increase in intraluminal pressure (pA2=8.68 and 7.02, respectively), while they did not affect endothelin-1-induced inhibition of spontaneous activity. Endothelin 1 produces increase in tone and intraluminal pressure of isolated human ureter acting on both ETA and ETB receptors, the first one being functionally more important. On ly endothelins 1 and 3 inhibit spontaneous, phasic activity of human ureter, but this effect was not blocked by selective antagonists of ETA and ETB receptors., S. M. Jankovic ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy