Pressure responses and conduction of peristaltic wave in guinea-pig ureter

Physiological properties of guinea-pig ureteral segments were studied by measuring the internal pressure responses to electrical stimulation in iso-volume conditions and by recording the contraction elicited by local electrical stimulation in iso-pressure conditions with a video-system. In iso-volume conditions, the phasic pressure response of the ureter increased in magnitude with increasing resting intra-luminal pressure and its threshold was lower in the proximal end, i.e., the part nearest to the renal pelvis, and higher in the distal end. In iso-pressure conditions, the average conduction velocity of the contraction wave was 2.30 +/- 0.54 cm/s (mean and standard deviation, n = 20) in the pressure range of 2-4 cmH2O, being slower in the proximal than in the distal ureter. The velocity decreased with increasing internal pressure. The velocity was nearly equal both in the normal direction of conduction and in the reverse one. The duration of the peristaltic contraction was longer in the proximal and shorter in the distal ureter. These results are discussed in connection with the fundamental mechanical properties of smooth muscle cells.