In vitro studies on human primary obstructed megaureters.

We studied isolated muscle strips from the dilated segments of primary obstructed megaureters from 2 children and 2 adults. The preparations were obtained at ureteral reimplantation procedures and mechanical activity was compared with that of normal ureteral segments obtained at tumor nephrectomies. In contrast to normal ureters, all the preparations of the megaureters of the children showed stable spontaneous phasic activity over several hours. The adult megaureters were inactive. In both tissues a marked tonic, sustained contraction could be induced by norepinephrine. This type of response is found in calyceal and pelvic tissues only in normal upper tracts. Normal ureters responded to norepinephrine with an increase in the frequency of spontaneous phasic contractions. The qualitatively different responses of the megaureters (in comparison to normal ureteral tissue) to alpha-adrenoceptor stimulation may be due to abnormal subcellular distribution of activator calcium in these hypertrophied tissues. The observed in vitro findings may be related to the radiographic observations of impaired and uncoordinated peristalsis in primary obstructed megaureters.