Pacemaker localization in the renal pelvis of the unicalyceal kidney. In vitro study in the rabbit

To determine the precise localization of the pacemaker in the renal pelvis of the unicalyceal rabbit kidney, the spontaneous activity of muscle strip preparations was investigated in vitro. (1) The highest frequency of spontaneous contractions was found in the most intrarenal part of the renal pelvis. (2) The frequency diminished from the most intrarenal parts to the pyeloureteral junction. (3) No spontaneous activity was observed in ureter preparations; even adrenaline, noradrenaline, acetylcholine and oxytocin did not start any contraction. In the pyeloureteral system the cells with the highest spontaneous frequency will act as a pacemaker. Cells with a less frequent activity can only work as secondary or latent pacemakers.