The pacemaker properties of the various regions of isolated segments of the rabbit renal pelvis were examined. The results show that pacemaker frequency and waveform of contraction change significantly within the renal pelvis. The highest frequency was encountered at the fornix, while the ureteropelvic junction is lowest.

There are regional variations of the amplitude, frequency and waveform of spontaneous contractions within the isolated renal pelvis and calyx of the multicalyceal pyeloureter of the pig. The contractility of these structures was studied in normal and hydronephrotic preparations. Tissues were obtained from normal and chronically obstructed animals. In 20 normal preparations, the contractile frequency of the renal pelvis was 4.9 ± 2.1 contractions/min, while that of the calyx was 9.5 ± 2.2 (mean ± SD). The recorded amplitude was 0.95 ± 0.92 and 0.45 ± 0.61 g, respectively. The waveform of the calyceal contractility approximated the sinusoid demonstrating a slow rise and fall in tension, while the waveform of renal pelvic smooth muscle demonstrated a faster increase in tension. Obstruction and hydronephrosis produced a minimal alteration in the frequency and amplitude of the calyceal structures, 9.1 ± 2.2 contractions/min and 0.71 ± 0.49 g, respectively. Hydronephrotic renal pelves demonstrated a significant increase in the frequency of spontaneous contractility 8.0 ± 4.2 contractions/min with no change in the mean amplitude of contraction 0.88 ± 0.90 g. These data suggest that obstruction alters the frequency of isolated renal pelvic contraction so that they approximate the frequency of isolated calyceal contractions.