Key result
Verapamil and nifedipine potently suppressed norepinephrine-induced phasic contractions in human ureteral muscle, but had little effect on tonic responses in the renal calyx and pelvis.
Different regions of the human upper urinary tract exhibit distinct contractile responses to norepinephrine and differential sensitivities to calcium channel blockers, suggesting separate calcium activation pathways.
Should not alter clinical management of upper tract disorders; leaves open regional CCB effects on human ureteral versus pelvic contractility.
The effects of the calcium channel blockers verapamil and nifedipine on norepinephrine-induced activation were studied in different tissues of the human upper urinary tract. In usually inactive ureteral muscle strips, norepinephrine induced predominantly phasic contractions with only minimal effects on resting tension. In contrast, in isolated segments of the renal calyx and pelvis, irrespective of preexisting spontaneous phasic activity, the same agonist effected a long-lasting tonic contraction. These different types of mechanical activity induced by norepinephrine showed different sensitivities to calcium channel blockers, phasic contractions being potently suppressed while the tonic response was little affected by the drugs. This different pattern of response to norepinephrine and the different sensitivity of the responses to calcium channel blockers suggest different and separate coupling mechanisms between the receptors involved and the calcium pools responsible for initiation of contraction. The existence of different calcium pathways activating the contractile proteins in the human upper urinary tract is postulated.
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Hertle et al. (1984) studied None (in vitro study of human upper urinary tract tissue). Verapamil and nifedipine was evaluated on Norepinephrine-induced activation (phasic and tonic contractions). Verapamil and nifedipine potently suppressed norepinephrine-induced phasic contractions in human ureteral muscle, but had little effect on tonic responses in the renal calyx and pelvis.
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