Vasopressin excitatory action on smooth muscle from human renal calyx and pelvis.

The motor response to vasopressin, a neuropeptide promoting the reabsorption of water, was isometrically investigated in vitro in human renal calyces and pelvis in relation to possible modulation of urinary flow by these tubular structures. Kidneys were obtained from nine male patients who underwent nephrectomy for either renal or ureteral cancer. Minor calyces and pelvis were carefully removed. Strips (10 mm x 3 mm) were cut from infundibular region of minor calyces and from renal pelvis and placed in 10 ml organ bath for isometric tension recordings. Calyceal and pelvic smooth muscle strips exhibited spontaneous phasic contractions which occurred with regular frequency and amplitude. Vasopressin induced a dose-dependent [10(-10) to 10(-6) M] enhancement of basal tone (P <0.01) and a decrease of spontaneous contractions on isolated strips from minor calyces and pelvis. The effect of vasopressin was inhibited by prior administration of D(CH2)5Tyr(Me)2-Arg8-Vasopressin antagonist [10(-7) M]. The excitatory response to vasopressin was Tetrodotoxin [TTX]-resistant and was not affected by pre-treatment with phentolamine [10(-5) M], atropine [10(-5) M], and hexamethonium [10(-5) M]. After incubation of the specimens in Ca2+-free medium containing EGTA [0.5 mM] or after treatment with nifedipine [10(-5) M], both spontaneous and vasopressin-induced contractions [10(-10) to 10(-6) M] were completely inhibited in all specimens. Our results can be interpreted to imply that the tonic contractions induced by vasopressin facilitate the reabsorption of water by increasing the hydraulic resistance of the tubular structures below collecting ducts.

Stimulation of calcium uptake by norepinephrine or high external potassium in human calyces and renal pelvis.

The effects of stimulation with either 10 mumol/l norepinephrine or 85 mmol/l extracellular potassium concentration on calcium uptake were studied in muscle strips from human renal calyces and from the renal pelvis. The apparent uptake of calcium under control conditions was essentially complete after 30 min. Stimulation of the muscle strips with norepinephrine or high external potassium significantly (P less than 0.05) increased the calcium uptake over the control values at 30 and 100 min, whereas 45Ca efflux was virtually not affected. It is concluded that the mechanical responses of the muscle strips to norepinephrine or high external potassium correspond with an increased uptake of calcium suggesting that both types of activation are mediated by an increase of intracellular calcium concentration similar to that described in other smooth muscles.

A double-blind study comparing the efficiency, tolerance and renal effects of iopromide and iopamidol.

A randomized double-blind, group comparative study was carried out to investigate the diagnostic efficiency and side-effect profiles, with particular reference to renal tolerance, of iopamidol and a newer non-ionic contrast medium iopromide, when used in excretory urography. The trial demonstrated that, in a population of 137 patients undergoing excretory urography and being investigated from baseline up to 2 weeks after the administration of the contrast medium, there were no significant adverse effects on the indicators currently thought to reflect renal function. The efficiency of the two contrast agents proved to be very similar and the radiographic quality of opacification was adequate in nearly every case.

Effects of prostaglandins on the isolated human minor calyx.

Effects of prostaglandins (PGE1, PGE2, PGF2 alpha, and PGI2) on the isolated human minor calyceal strips were isometrically investigated in vitro. PGE2 and PGF2 alpha, 10(-7) to 10(-6) g/ml, increased the basal tone of spontaneous contractions. PGE1 and PGI2 did not affect the contractions of the isolated human minor calyceal strips. The increases on the basal tone induced by PGE2 and PGF2 alpha were not affected by the pretreatment with atropine, hexamethonium, and phentolamine. Following incubation in a Ca2+-free medium, spontaneous contractions and the responses to PGE2 and PGF2 alpha were abolished. The results suggest that the contractile effects of PGE2 and PGF2 alpha may not be mediated by activation of muscarinic, nicotinic, or alpha-adrenergic receptors and result from a consequent increase of the transmembrane Ca2+ influx.

Calcium channel blockade in smooth muscle of the human upper urinary tract. I. Effects on depolarization-induced activation.

The effects of the calcium blockers nifedipine, verapamil, D600 and diltiazem on mechanical activity were studied in isolated preparations of the human upper urinary tract. Two types of activity were used: spontaneous phasic-rhythmic activity in calyceal segments and potassium-induced depolarization in ureteral muscle strips. Nifedipine (10(-6) mol./l.), verapamil, D600 and diltiazem (all 10(-5) mol./l.) completely suppressed spontaneous phasic-rhythmic activity. Elevation of extracellular potassium concentration induced contractions concentration-dependently. A log-linear relationship between the extracellular calcium concentration and the 85 mmol./l. potassium-induced activation was demonstrated. Concentration-response relationships of the compounds were found by activating the muscle strips with 85 mmol./l. potassium in the Tyrode solution. This activation model produced stable and reproducible contractures. The compounds antagonized depolarization-induced activations concentration-dependently, nifedipine being the drug with the lowest EC50 value; its relative potency with reference to papaverine was about 8,000 to 1. The order of potency of the other drugs was in the following sequence: D600 greater than verapamil greater than diltiazem. It is concluded that processes in the human upper urinary tract which are triggered by depolarization (action potential or high potassium concentrations) are highly sensitive to calcium channel blockers.

Calcium channel blockade in smooth muscle of the human upper urinary tract. II. Effects on norepinephrine-induced activation.

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.

Effects of beta-adrenergic agents on the pacemaker of ureteral peristalsis.

An electromyographic study of the responses of the pelvicalyceal border which is the pacemaker region of ureteral peristalsis, and of the renal pelvis and ureter to dobutamine and terbutaline, beta 1- and beta 2-adrenergic stimulants, respectively, was performed using isolated canine pelviureteral preparations. The beta 1-adrenergic stimulant produced a marked enhancement of discharge potential in the pacemaker region, but, in the renal pelvis and ureter, it did not evoke any noticeable response. Application of the beta 2-adrenergic stimulant led to disappearance of discharges in the renal pelvis and ureter, whereas the pacemaker region continued to exhibit regular discharges. These findings seem to suggest the presence in the pelvicalyceal border of a group of cells which, unlike other smooth muscle cells, respond to beta-adrenergic agents in a fashion similar to the cardiac pacemaker, namely, stimulated by beta 1-adrenergic stimulants and not inhibited by beta 2-adrenergic stimulants.

Effects of some autonomic drugs on the isolated human minor calyx.

The effects of some autonomic drugs on the isolated human minor calyceal strips were investigated quantitatively. Norepinephrine, epinephrine and phenylephrine dose dependently increased the basal tone and the frequency of spontaneous contractions and decreased their amplitudes, which were depressed by phentolamine. Acetylcholine at high doses increased the basal tone and decreased the amplitude, which were depressed by atropine without changing the frequency. These findings indicate the existence of alpha-adrenoceptors and muscarinic receptors in the human minor calyceal smooth muscles.

[The effect of pentazocine on pyelo-ureteral activity. A radiological study (author's transl)]. / Effetti della pentazocina sulla attività pielo-ureterale. Studio radiologico.

Following 30 mg pentazocine lactate intravenous in the course of perfusion urography in 20 patients, changes in the amplitude and motor activity of the calicopyelic cavities were noted on a television circuit and spot-films were taken. An early and protracted increase in ureteral peristaltic activity was shown. A number of examples of this are presented.

In vitro studies on the human renal calices.

Smooth muscle preparations taken from the minor calices of human kidneys were investigated by an isolated tissue technique. The existence of alpha-adrenoceptor and muscarinic receptor sites were demonstrated and it was shown that stimulation with the appropriate agonist resulted in an excitatory response. No evidence could be found to support the presence of beta-adrenoceptors in such tissues. The results of transmural electrical stimulation of similar preparations were highly suggestive of an effective innervation of the alpha-adrenoceptors.