The influence of the rapid rise of intraluminal pressure of the upper urinary tract on ureteral action potentials

Abstract

The present investigation was undertaken in order to examine the ureteral action potentials following transient rapid rise of the intraureteral pressure. In 21 adult mongrel dogs, physiological saline and 5% formalin were injected into the left and right obstructed ureters, respectively to produce rapid rise of intraureteral pressure to 60 cmH2O for 7 minutes, and then ureter was released from obstruction. In these experiments, recordings of ureteral electromyogram and intraureteral pressure were made. Histological changes of pelvi-ureteral system were also observed microscopically. Results 1. After injection of physiological saline, discharge intervals were significantly shortened, but normal discharge intervals were restored when the ureters were released from obstruction. Under conditions of reobstruction, the discharge intervals were shortened and intraureteral pressure inducing the shortest discharge interval was 50 cmH2O. 2. After injection of formalin, discharge intervals were significantly shortened, and the action potentials disappeared in 1 minute 28 seconds to 4 minutes 51 seconds after the injection in 18 out of the 21 ureters. No discharge was observed at 7 minutes after the injection in 16 out of the 18 ureters. In 14 out of the 16 ureters, however, the action potentials were restored when the ureters were released from obstruction or after the obstruction was readministered. Under conditions of reobstruction, discharge intervals were shortened, and intraureteral pressure inducing the shortest discharge interval was 20 cmH2O. 3. Histologically, the loss of epithelium, as well as edema and vasodilatation in lamina propria, were observed only in the mucosa of the middle portion of the ureters receiving formalin. The results of the present study show that a transient rapid rise of intraluminal pressure of the upper urinary tract caused by the injection of physiological saline or formalin, dose not have a significant effect on the ureteral action potentials, and that disappearance of the action potentials is refered to pharmacological action of formalin.