Abstract
Background and Purpose: The aim of this study was to establish a model in which pressurized segment of ureter was assessed in organ chamber. Methods: Predetermined and constant intraluminal pressures were maintained by an automatically controlled pumping system. Contractions were induced by gradually distending the ureter, the minimal intraluminal pressure to induce ureteral contractions averages 15 mmHg in 4-cm long porcine ureters. Results: Frequency of contractions increased, while the amplitude of contractile waves decreased when the intraluminal pressure increased. Electrical stimulation (0.8 msec, 10 volts, 8 Hz) elicited ureteral contractions in all specimens. Contractions induced by electrical stimulation were frequency dependent, and were not affected by atropine, bretylium or tetrodotoxin. Norepinephrine (from 10^(-7) M to 10^(-4) M) caused concentration dependent ureteral contractions. High concentration of the ganglionic stimulator (3×10^(-4) M, 1, 1-dimethyl-4-phenyl-piperazinium iodide) induced continuous ureteral contractions which could be inhibited by phentolamine (10^(-4) M) but not by atropine (10^(-4) M). Adenosine triphosphate (ATP), from 10^(-4) M to 10^(-2) M, elicited contractile waves whose patterns differed with those of the norepinephrine-induced contraction. After administration of ATP, the intraluminal pressure reached a plateau and then declined gradually. Extraluminal NO donors (S-nitroso-N-acetyl cysteine) inhibits norepinephrine or DMPP-induced ureteral contractions. Conclusion: By pressurizing the ureter to keep the contractile property constant, the contraction of an intact ureter can be observed in a sensitive and stable manner. And the intraluminal or extraluminal effects of different drugs can be assessed reliably in this model.
Published Version
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