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PubMed1991

Do renal tubular dopamine receptors mediate dopamine-induced diuresis in the anesthetized cat?

The aim of this study was to investigate whether the pentobarbitone anesthetized cat is a suitable preparation in which to characterize renal tubular dopamine receptors. Intravenous infusion of dopamine (10-100 micrograms/kg/min) resulted in a dose-related increase in mean blood pressure (MBP), urine output, sodium excretion (UNaV), and fractional sodium excretion (FENa). This diuretic effect occurred despite little change in glomerular filtration rate, suggesting that it is a consequence of decreased tubular reabsorption. Dopamine (10-100 micrograms/kg/min, i.v.) also induced marked dose-related falls in renal vascular conductance; however, renal blood flow was not significantly reduced. The increases in MBP, urine output, UNaV, and FENa induced by dopamine (10-100 micrograms/kg/min, i.v.), were unaffected by pretreatment of cats with either the selective dopamine DA1 or DA2 receptor antagonists, SCH 23390 (30 micrograms/kg, i.v.), or domperidone (100 micrograms/kg, i.v.) respectively. In contrast, pretreatment of cats with the nonselective alpha-adrenoceptor antagonist, phentolamine (1 mg/kg, i.v.) prevented dopamine-induced increases in urine output and MBP. Infusion of the selective dopamine DA1 receptor agonist fenoldopam (0.01-10 micrograms/kg/min) into the left renal artery failed to increase left renal vascular conductance, or left kidney urine output, UNaV, or FENa. In conclusion, this study provides no evidence for the involvement of renal tubular dopamine receptors in dopamine-induced diuresis in anesthetized cats. Rather, the diuretic effect appears to be linked to stimulation of alpha-adrenoceptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2005

Renal pelvis volume during diuresis in children with hydronephrosis: implications for diagnosing obstruction with diuretic renography.

PURPOSE: We measured the volume of the renal pelvis during diuretic renography (DR) in children with normal and hydronephrotic kidneys to determine if changes in pelvic volume could affect the accuracy of DR in diagnosing obstruction. MATERIALS AND METHODS: We studied 18 patients 1 month to 10 years old with unilateral hydronephrosis ultimately proved to be either obstructive or nonobstructive. Simultaneous DR and ultrasound were performed with patients supine using the gamma camera. Ultrasound measurements of the renal pelvis in 3 dimensions, obtained before and at intervals after diuretic injection, were used to calculate renal pelvic volume. The contralateral normal kidneys were used as controls. RESULTS: Between 15 and 60 minutes after diuretic injection the renal pelvis enlarged to a maximum volume in all hydronephrotic and normal kidneys and then gradually decreased in size. Mean average increase in volume for hydronephrotic kidneys ranged from 46% in obstructed kidneys to 88% in nonobstructed kidneys. Volume expansion caused dilution of isotope within the renal pelvis, which resulted in prolongation of elimination half-time (T1/2) in 42% of nonobstructed hydronephrotic kidneys sufficient to register an obstructed washout pattern. However, there were no differences in the initial pelvic volume or the rate or extent of increases or decreases in pelvic volume that would permit nonobstructed hydronephrotic kidneys to be distinguished from obstructed ones. CONCLUSIONS: The renal pelvis enlarges during diuresis in children with hydronephrosis. This enlargement causes dilution of isotope within the renal pelvis during DR, which prolonged the isotope washout rate or T1/2 sufficiently to produce an obstructed washout pattern in more than 40% of hydronephrotic kidneys that were ultimately proved to be nonobstructed. This misdiagnosis of obstruction is particularly likely to occur in children younger than 2 years because pelvic volume expansion is so exaggerated. Consequently, T1/2 appears to be particularly vulnerable to inaccuracy in diagnosing obstruction in this age group, and, therefore, it should not be relied on as an operative determinant.

Child↗
PubMed1980

Renal handling of urate in healthy man in hyperuricaemia and renal insufficiency: circadian fluctuation, effect of water diuresis and of uricosuric agents.

To differentiate between extrarenal and renal causes of hyperuricaemia and gout, clearances of urate and creatinine were monitored for 3 1/2 days in fifty-two individuals (seven with a history of gout) with no gross impairment of renal function (creatinine clearance 52-137 ml/min). Dietary purine intake was kept constant. Monophasic circadian fluctuations of fractional urate excretion (= urate clearance over creatinine clearance) were observed with peak values in the afternoon, about 50% higher than during the night. Circadian fluctuations of urinary flow rate were almost identical. However, enhancement of urinary flow rate due to water diuresis had no effect on urate clearance. Despite wide variation of plasma urate concentrations among different individuals (+/- 30% SD), daily urate excretion varied little (+/- 4% SD) and did not correlate with plasma urate (r = 0.03). Thus extrarenal factors appear not to account for the occurrence of hyperuricaemia in these patients. In contrast, a clearcut negative correlation was apparent between plasma urate concentration and fractional urate clearance (r = 0.72), which could fully account for the variations of plasma urate concentration. To elucidate further the mechanism responsible for antiuricosuria in hyperuricaemic patients, the effects of the uricosuric agents benzbromarone and probenecid were tested. A clearcut correlation was apparent between control fractional urate excretion and uricosuric effect of both benzbromarone and probenecid (r = 0.83 and 0.88, respectively), suggesting that anti-uricosuria was due to defective secretion. In an additional series, the uricosuric effect of probenecid was tested in ten patients with renal insufficiency. In these patients the uricosuric effect was clearly blunted, indicating that urate reabsorption is reduced in renal insufficiency.

Adult↗
PubMed1988

Arginine vasopressin dissociates the diuresis and natriuresis due to atrial natriuretic factor in man.

The possible interaction between arginine vasopressin (AVP) and atrial natriuretic factor (ANF) in the control of urinary sodium and water excretion was investigated in man. Nine healthy male volunteers undergoing stable maximal water diuresis were studied on four separate occasions. Atrial natriuretic factor 15 pmol kg-1 min-1 or placebo (P) was concomitantly administered against a background infusion of either AVP 0.003 pmol kg-1 min-1 or P; thus the combinations P + P, AVP + P, P + ANF and AVP + ANF were studied. Atrial natriuretic factor caused a significant increase in sodium excretion (UNaV) [+56%], urinary flow rate (V) [+17%] and free water clearance (CH2O) [+23%]; creatinine clearance (Ccr) did not change. Arginine vasopressin reduced V (-58%) and CH2O (-68%) but did not alter UNaV or Ccr. On the AVP + ANF study day, UNaV increased (+64%) as with P + ANF, but V (-44%) and CH2O (-52%) continued to decrease below baseline levels; analysis of variance showed this antidiuresis reflected the prevalent effect of AVP rather than any specific interaction. These results show that AVP is able to dissociate the natriuretic and diuretic effects of ANF.

Adult↗
PubMed1983

Post-obstructive diuresis.

A patient with post-obstructive diuresis is described. Inappropriate losses of salt and water occurred, with urine volume exceeding half the glomerular filtration rate. Additionally, excessive urinary excretion of potassium, bicarbonate, calcium, phosphate, magnesium and urate took place in the presence of subnormal blood levels. Transient proteinuria was also observed. This case demonstrates that serious electrolyte disturbances can occur after relief of urinary tract obstruction and the evidence suggests these may be due to disordered proximal tubule function.

Diuresis↗
PubMed1982

Idiopathic hydronephrosis in childhood--a comparison between diuresis renography and upper urinary tract morphology.

Twenty-seven children undergoing surgery for suspected pelviureteric junction obstruction were studied by pre-operative diuresis renography. The results obtained by this test were compared with histological and histochemical studies of the resected specimens of renal pelvis. A significant correlation was found between these methods of assessment. In addition, the morphological appearances of the renal pelvis tended to show more marked changes in the younger children.

Adolescent↗
PubMed1986

Predictive value of 99mTc-DTPA renography studies under conditions of maximal diuresis for the functional outcome of reconstructive surgery in children with obstructive uropathy.

Renographic studies under standardised conditions of maximal diuresis provoked by infusion of hypotonic saline and frusemide were made on 51 patients with 54 dilated upper urinary tract systems in order to distinguish obstructed from non-obstructed systems. Of the 23 systems judged on clinical and radiological grounds to be obstructed only 12 were in fact obstructed following infusion of hypotonic saline and frusemide. In 10 of these systems (10 patients) an Anderson-Hynes pyeloplasty was carried out. All systems showed improved renal function after operation and the renographic pattern became non-obstructed.

Adolescent↗
PubMed1989

Assessment of the nephron segments involved in post-obstructive diuresis in man, using lithium clearance.

The phenomena of post-obstructive diuresis and natriuresis have been studied using the lithium clearance technique in 10 patients with high pressure chronic retention. Following relief of obstruction there was a significant increase in both sodium and water excretion. There was a coincident reduction in the fractions of sodium and water reabsorbed in both proximal and distal nephron segments. This study demonstrates for the first time that following relief of chronic obstructive uropathy in man, changes in sodium and water excretion are due to altered handling in both proximal and distal nephron segments.

Aged↗
PubMed1961

Diuresis in rats: effects of sympathomimetic and sympathetic blocking agents.

Dopamine and tyramine possess diuretic properties resembling but weaker than those of noradrenaline in the rat. These three amines produce a relatively smaller loss of sodium than does adrenaline. Bretylium shows a diuretic action which is apparently associated with its sympathomimetic properties and which is antagonized by phenoxybenzamine. However, bretylium causes a relatively greater loss of potassium and chloride than do the sympathomimetic amines. A slight antidiuretic action is shown by bretylium after its diuretic effect has subsided and a similar effect is produced by BW 172C58, which has relatively weak sympathomimetic properties. In contrast to these adrenergic neurone blocking agents, phenoxybenzamine and a ganglion blocking agent (pentacynium) show powerful antidiuretic effects. These observations are consistent with the view that the adrenal medulla has an important role in facilitating water diuresis in rats.

Adrenergic Agents↗
PubMed1961

Effect of L-tryptophan on diuresis and 5-hydroxyindoleacetic acid excretion in the rat.

Oral administration of L-tryptophan to rats produced two main biochemical and pharmacological effects: a marked increase in urinary 5-hydroxyindoleacetic acid excretion, and a significant reduction in the urine flow after a water load. Urinary 5-hydroxyindoleacetic acid excretion reached its maximum 2 to 6 hr after the administration of tryptophan, and it increased with the dose of the amino acid. Antidiuresis was seen after the administration of L-tryptophan, 200 mg/kg, or more. The effect appeared promptly and it was roughly proportional to the dose of the amino acid administered. Both antidiuretic effect and increase in urinary 5-hydroxyindoleacetic acid excretion were more intense after oral than after parenteral administration of L-tryptophan. D-Tryptophan, in oral doses up to 1,000 mg/kg, produced neither an increase in urinary 5-hydroxyindoleacetic acid nor a reduction of diuresis. Available evidence suggests that reduction of urine flow is a consequence of biosynthesis and release of 5-hydroxytryptamine by the gastrointestinal mucosa. Tryptamine produced by direct decarboxylation of L-tryptophan does not seem to play any important role.

Administration, Oral↗
PubMed1970

Renal tubular flow dynamics during angiotensin diuresis in the rat.

1. Tubular size and lissamine green transit times were measured in rat kidneys undergoing a diuretic response to angiotensin II (0.5 mug/kg per min), and compared with the changes observed during diuresis induced by osmotic diuretics, noradrenaline and chlorothiazide.2. Angiotensin always caused a marked prolongation in proximal and distal tubular transit times; individual distal convolutions were coloured for prolonged periods, and lissamine green appeared in high concentration in distal tubules.3. Marked changes were observed in superficial tubular calibre during a stable diuretic response to angiotensin. Where distal tubular diameter was normal for the rate of urine flow, proximal tubular volume was generally reduced. In a number of experiments, however, distal tubules were markedly dilated, and in these cases proximal tubular volume was also often increased. Angiotensin may therefore be capable of causing a degree of internal hydronephrosis in the rat kidney.4. Prolongation of dye transit times, and the appearance of a concentrated lissamine green bolus in distal tubules, was suggestive of a decreased superficial nephron flow rate, indicating that the diuretic effect of angiotensin may take place only through deeper nephrons.

Angiotensin II↗
PubMed1983

Dose-dependent reduction in renal magnesium clearance by amiloride during frusemide-induced diuresis in rats.

The effects of the potassium-sparing diuretic, amiloride, on fractional magnesium excretion were investigated at four doses (0.02, 0.08, 0.20 and 2.00 mg kg-1 h-1) during frusemide-induced diuresis. Amiloride caused a dose-dependent reduction in the fractional excretion of both magnesium and potassium, whereas the effects of amiloride, over the same dose range, on fractional sodium and calcium excretion were not dose-dependent. The results indicate that amiloride exerted a specific renal action to alter magnesium and potassium transport dissociated from effects on sodium excretion.

Amiloride↗
PubMedDate not supplied

ECG changes in response to diuresis in an ambulatory patient with congestive heart failure.

This case report describes an ambulatory patient with congestive heart failure and peripheral edema who lost 18 lb in response to enhanced diuresis over the course of 1 week. The ECG showed increases in the amplitude of P waves, QRS complexes, and T waves; the duration of P waves, QRS complexes, and QT intervals; and the dispersion of P and QT. The clinical implications of these ECG changes are discussed.

Ambulatory Care↗
PubMed1981

Investigation of the role of kidney kallikrein on bumetanide induced diuresis in rats.

Administered to anaesthetized, laparatomized rats bumetanide (10 mg/kg intravenously) evoked a rapid and large diuretic response. This was associated with three to five fold enhancements of urine kallikrein (kininogenase) excretion. In addition bumetanide slightly decreased (approximately 10 mmHg) the blood pressure and temporarily increased renal blood flow (less than 10%). The capacity of bumetanide to increase urine kallikrein excretion was inhibited either by pretreatment with chlorazanil (3 mg/kg intravenously) or by the infusion of aprotinin (5000 KIE/kg/min). Kallikrein inhibition did not significantly modify bumetanide induced diuresis, natriuresis, kaliuresis, lowering of blood pressure or renal vasodilating effect.

Animals↗
PubMed1984

Diuresis and urine concentration during CPAP in newborn infants.

The impact of continuous positive airways pressure (CPAP) on diuresis and urine concentration was studied in newborn preterm infants with respiratory insufficiency with and without pulmonary X-ray changes. Urine output and osmolality, sodium balance and blood pressure were measured before, during and after CPAP application. In all infants urine osmolality rose and urine output decreased significantly when high CPAP (8 cm H2O) was applied, especially in infants without radiographic pulmonary changes. Three infants also developed hyponatremia at high CPAP levels. The results indicate that high CPAP levels per se may affect fluid balance inadvertently. Therefore fluid intake and urine output should be monitored closely during CPAP treatment.

Blood Pressure↗
PubMed1989

Role of atrial natriuretic peptide in the diuresis of a newborn infant with the syndrome of inappropriate antidiuretic hormone secretion.

A fullterm infant had fetal distress and stained amnion. He underwent an exchange blood transfusion at 12 hours after birth because of hyperbilirubinemia. He developed oliguria combined with high urine osmolality during the first 27 hours of life despite normal creatinine clearance. The diagnosis of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) was made on the basis of high urine osmolality, low plasma osmolality and elevated plasma arginine vasopressin (AVP) concentration. We determined the plasma atrial natriuretic peptide (ANP) concentration for the first 4 days of life. After 27 hours after birth, urine volume increased while plasma AVP concentration remained high. On the other hand, plasma ANP concentration gradually increased after 27 hours of life. We speculate that ANP may play an important role in producing the spontaneous diuresis in the newborn infant with SIADH.

Atrial Natriuretic Factor↗
PubMed1976

Studies of cerebral osmoreceptors in anesthetized dogs: the effect of intravenous and intracarotid infusion of hyper-osmolar sodium chloride solutions during sustained water diuresis.

The function of the suggested hypothalamic osmoreceptors was investigated in dogs during light chloralose anesthesia. The dogs were subjected to an i.v. load of 40 ml/kg b.w.t. of a hypo-osmolar solution of sodium chloride and glucose. This degree of hydration was kept constantly by a specially constructed servo system based on the weight of the animal. During water diuresis the renal free water clearance remained essentially constant for several hours (mean about 0.2 ml/kg b.w.t. min). Renal sodium excretion was low (mean 0.82 mumol/kg b.w.t. min) and decreased continuously throughout the experimental period. I.v. infusion of hyperosmolar sodium chloride solution (1.33 mmol/kg b.w.t. in 30 min) was followed by prolonged parallel increases in free water clearance and sodium excretion, without any detectable change in the excretion of osmoles and potassium. The renal response to bilateral infusion of hyper-osmolar NaCl (1.33 mmol/kg b.w.t. in 30 min) into the common carotid arteries was identical to the response to i.v. infusion. The estimated increase in the osmolality of the carotid blood was 2.2%. In seven out of eight experiments intracarotid infusion of NaCl (1.33 mmol/kg b.w.t. in 8 min) did not elicit any reduction in free water clearance. On the contrary, an increase was found similar to that obtained after i.v. infusion. The estimated increase in the osmolality of the carotid blood was 8.4%. The present results question the validity of the currently held view that hypothalamic osmoreceptors play an important role in the control of the osmolality of plasma.

Animals↗