Topological localization of the frequency and amplitude characteristics of the whole and segmented renal pelvis

The contractile characteristics of pacemaker regions in the unicalyceal renal pelvis of the rabbit were examined in vitro. The amplitude and frequency spectra of spontaneous contractions of whole and separated circular and longitudinal renal pelvic strips were identified. The effect of stretch on these parameters were examined in order to establish whether the pacemaker region that generates contractions in the renal pelvis was sensitive to distention. The results show that the frequency of spontaneous contractions in the whole pelvis (65 +/- 18 mHz) was significantly higher than any part of the circularly (41 x 8 mHz) or longitudinally cut (43 +/- 8 mHz) pelvis. The amplitude of longitudinal strips, 52 +/- 11 mg, was significantly smaller than that of the circular strips, 267 +/- 52 mg. In the circularly separated pelvis the frequency of spontaneous contractions was highest in the proximal part (41 +/- 8 mHz) and lowest in the pelviureteral junction (8 +/- 1 mHz). No significant increase in frequency was seen upon stretch in the whole or separated pelvis although there was a decrease in the amplitude of both the whole and separated pelvis. These results show that the frequency of contraction of the whole or the segmented renal pelvis is not sensitive to stretch.