Pacemaker Process of Ureteral Peristalsis in Multicalyceal Kidneys

Abstract

The mechanical activity of isolated strips from different areas of the pyeloureteral system was investigated in 10 pigs: calyx, renal pelvis, pyeloureteral junction and ureter. Additionally, electrical activity was measured in some pyeloureteral preparations using the sucrose-gap technique. Regular spontaneous activity with an average frequency of 9.5/min was recorded in calyceal strips, decreasing to 5.4/min in renal pelvis, 5.7/min in pyeloureteral preparations and to 1.2/min in ureteral preparations. The activity of renal pelvis, pyeloureteral and ureteral preparations was less regular, and bursts of fast activity (near 10/min) could be observed in all these preparations. The membrane potential of pyeloureteral strips showed spontaneous generator oscillations of about 10/min. Variations in the pattern of ureteral peristalsis are due to different coupling ratios of membrane potential oscillations to contractions. Adrenaline (10^––5 mol/l) increased the frequency of the oscillations and enhanced their manifestation in the mechanical recordings, whereas tetraethylammonium (5–20 mmol/l) only increased the coupling ratio. The following concept for the generation of ureteral peristalsis in multicalyceal kidneys is developed: several (primary) oscillators exist in the calyces; in the pyeloureteral junction a (secondary) pacemaker exists which has an intrinsic frequency similar to that of the calyceal pacemakers; both processes cooperate in the generation of ureteral peristalsis.

Interstitial cell of Cajal-like cells in the upper urinary tract

“…It has been envisaged that these atypical SMC drive neighbouring 'typical' SMC in the renal pelvis either directly [16,33] or indirectly [33]. A 'coupled linear oscillator' model of multiple pacemaker regions, envisages that the most proximal pacemaker regions fire at the greatest frequency [19,51]. Increased diuresis or wall distension have been suggested to increase the coupling between neighbouring pacemaker regions and induce the summation of this asynchronous activity to trigger action potential discharge and renal pelvis contraction at a frequency driven by the most proximal pacemaker region present [2,3,19,51].…”

“…A 'coupled linear oscillator' model of multiple pacemaker regions, envisages that the most proximal pacemaker regions fire at the greatest frequency [19,51]. Increased diuresis or wall distension have been suggested to increase the coupling between neighbouring pacemaker regions and induce the summation of this asynchronous activity to trigger action potential discharge and renal pelvis contraction at a frequency driven by the most proximal pacemaker region present [2,3,19,51]. However, simultaneous extracellular recordings from numerous sites on the sheep renal pelvis have revealed that only one pacemaker region on the pelvi-calyceal border is active at any one time and that the pathway of conduction might meander throughout the renal pelvis.…”

Gap Junctional Communication and Vascular Smooth Muscle Reactivity: Use of Tetraethylammonium Chloride

“…TEA is a putative activator of gap junction complex formation [10,11] and in both ves sels examined -tail artery and mesenteric artery -TEA induced oscillatory contractions. The pacemaker-like ac tivity induced by TEA has been observed in nonvascular smooth muscle [10,20] and is associated with an increase in gap junction number as measured by electron micros copy [10]. This activity is probably not solely the result of potassium channel blockade, a better known activity of TEA, as the concentrations used to induce oscillatory con tractions are significantly above those used to block potas sium channels [21], Furthermore, the lag (minutes) be tween addition of TEA and appearance of contractile oscillations is not characteristic of potassium channel blockade [21], but is most likely necessary for recruitment of gap junction complex formation.…”

Inhibition of Human and Pig Ureter Motility in Vitro and in Vivo by the K+ Channel Openers PKF 217-744b and Nicorandil

“…The origin of ureteral peristalsis in intact ureters is thought to be from a main pacemaking area in the pelvicalyceal border which has the steepest depolarization (Dixon and Gosling, 1973;Hannappel et al, 1982;Hanke et al, 1992;Lammers et al, 1996). Klemm et al (1999) thoroughly investigated the cells underlying pacemaker activity in the guinea pig upper urinary tract.…”

“…Furthermore, he suggested that ICC-like cells, cells morphologically similar to the intestinal "interstitial cells of Cajal", in the renal pelvis and the pelvicalyceal junction play an integrative role by acting as a conduit for the electrical signals of the pacemaker cells to the smooth muscle cells of the renal pelvis and the ureter (Klemm et al, 1999). Indications of spontaneously active smooth muscle cells present in the porcine urinary tract distal to the renal pelvis or the ureteropelvic junction have been reported before (Hannappel et al, 1982). In isolated ureter rings, the spontaneous activity could originate from solitary pacemaker cells whose own spontaneous activity would be subordinate to the pelvicalyceal pacemaking system in the intact urinary system.…”