Increased Urine Flow Rate Research Articles

Prostaglandin-dependent polyuria in hypercalcemia.

The present experiments examined the role of prostaglandin biosynthesis in the increase in urine flow rate seen in rats with hypercalcemia induced by the administration of 1,25-dihydroxycholecalciferol. In a first group, rats receiving the vitamin D metabolite developed hypercalcemia, polyuria, and increased urine prostaglandin E excretion. Indomethacin resulted in a fall in urine prostaglandin E excretion. A second group was fluid restricted to ascertain whether increased thirst could be an etiologic mechanism of the polyuria. This resulted in a trivial fall in urine flow rate despite a fall in body weight and a rise in both urine and plasma osmolality. In a final group, prostaglandin inhibition restored the vasopressin sensitivity of the hypercalcemic kidney. Accordingly, the polyuria seen in hypercalcemic rats after the administration of 1,25-dihydroxycholecalciferol is associated with an increase in urine prostaglandin E excretion and can be reversed by inhibition of prostaglandin synthesis. In addition, this polyuria can occur independent of the thirst mechanism. Finally, there is evidence that the vasopressin resistance of the hypercalcemic kidney could be reversed by prostaglandin inhibition.

Acute effects of intravenous furosemide administration on serum digoxin concentration

The effect of intravenous (IV) furosemide (2.5 mg/kg) on serum digoxin concentration, urine flow rate, and myocardial contractility and rhythm was studied in normal dogs and dogs treated with digoxin. Furosemide IV to animals which had not been receiving digoxin resulted in increased urine flow rate from 0.11 ± 0.03 to 0.43 ± 0.1 ml/min/kg, but had no effect on myocardial contractility, blood pressure, or cardiac rhythm. Furosemide IV to animals with steady-state therapeutic serum concentrations of digoxin (2.0 ± 0.58 ng/ml) increased urine flow similarly but did not significantly alter serum digoxin concentration, blood pressure, myocardial contractility, or cardiac rhythm. Thus, contrary to some previous reports, furosemide does not interact with digoxin to produce an elevation in serum digoxin concentration or enhancement of the glycoside's myocardial action.

330 INFLUENCE OF BIOLOGICAL MATURATION ON THE DETERMIN-ANTS OF RESPONSE TO FUROSEMIDE

The effect of age on the determinants of the diuretic response to furosemide was evaluated in 22 infants (9 premature infants 2-6 days old and 13 infants 1 to 36 months old). The urinary excretion of furosemide, and therefore the presentation of the drug to its site of action, was significantly slower (p < 0.005) in the premature infants (t½ = 26.5 ± 31.2 h) than in the older children (t½ = 1.79 ± 1.26 h). Despite the prolonged time of drug excretion, the younger infants excreted significantly less of the administered dose in the urine (20.7 ± 17.5% vs. 49.2 ± 22.9%; p < 0.01). All but one infant in each group exhibited an increase in urine flow after furosemide administration and demonstrated a linear relationship between furosemide excretion rate and diuretic response. The increase in urine flow rate per unit furosemide excretion rate was significantly greater in the premature infants (p < 0.001). The results suggest that the immaturity in at least two aspects of renal function contribute to the pattern of diuretic response seen in very young infants. Immaturity of organic ion transport limits the rate and amount of drug reaching its site of action. However, the inability of parts of the tubule not effected by the diuretic to compensate for the increased electrolyte and water loss leads to an enhanced sensitivity to the drug which is excreted.

Effects of sodium and chloride on potassium transport by the bullfrog kidney.

We have studied the effect on K transport of reductions in the Na and Cl concentrations of solutions perfusing the isolated bullfrog kidney. We used recently developed techniques for estimating the unidirectional reabsorptive and secretory K fluxes. Reduction of Na and Cl concentrations in the arterial perfusate from 112 and 100 mM to 22 and 10 mM, respectively, inhibited K secretion 82% and K reabsorption 97%. Reduction of only the Na concentration inhibited K secretion 42% but did not affect K reabsorption. Arterial and portal perfusion with 37 mM Na, 23 mM Cl reduced urine Na concentration to 6 mM and Na reabsorption by 59%. However, K secretion rose 88% and reabsorption fell 76%. Arterial and portal perfusates with 37 mM Na, 100 mM Cl reduced urine Na concentration to 2 mM and Na reabsorption by 46%. Still, K secretion was elevated 57% by an increase in urine flow rate. K reabsorption was not reduced. Arterial and portal perfusates with 112 mM Na, 23 mM Cl, and containing SO4 also stimulated K secretion 26% and inhibited K reabsorption 91%. Thus, reduction of perfusate Na concentration to 22 mM inhibited secretion but 37 mM was sufficient to permit stimulation of secretion by low Cl concentrations and by increased tubular fluid flow rate. Reduction of the perfusate Cl concentration stimulated secretion and inhibited reabsorption. We conclude that a minimum level of Na reabsorption is required to maintain K secretion, but above that minimum level changes in the rate of Na reabsorption do not affect the rate of K secretion. The tubular fluid Cl concentration or the rate of Cl reabsorption affects both reabsorption and secretion of K and, therefore, may be an important regulator of the rate of K excretion.

Acute effect of high dose (48 mg) of piretanide in advanced renal insufficiency.

1 The acute effects of a high dose of piretanide, a new potent diuretic were studied in eight patients with severely impaired renal function (GFR between 0.09 and 0.17 ml s-1 1.73 m-2). 2 After hydration and following two control periods, a single dose of 48 mg piretanide was ingested. Thereafter, urine was collected every 30 min for 2 h and every hour for the next 4 h. Urinary fluid losses were replaced orally (100 ml of water ever hour) and intravenously (isotonic saline + glucose infusion). 3 The following measurements were made: urine flow rate, clearances of inulin, PAH, urea, creatinine, uric acid, osmolar and free water clearances, excretion rates of sodium, chloride, potassium, calcium, phosphate, bicarbonate, ammonium, titratable acidity and urine pH. 4 Piretanide (48 mg) appeared to be effective in advanced renal insufficiency, producing a significant increase in urine flow rate, in sodium, chloride, potassium and calcium excretion and in Cosm. 5 There was no significant change in GFR, as measured by inulin clearance, or in the other measured parameters.

Effects of sodium orthovanadate on whole kidney and single nephron function

The renal effects of sodium vanadate (Na3VO4), an inhibitor of sodium-potassium-ATPase recently shown to be a potent diuretic, were studied by using clearance and micropuncture techniques in nondiuretic anesthetized rats. Administration of 1.0 mumole of sodium vanadate (high dose) increased urine flow rate (V) from 9.8 +/- 1.4 to 17.5 +/- 4.0 microliter/min (mean +/- SEM, P < 0.025), UNaF from 1.73 +/- 0.36 to 3.05 +/- 0.65 microEq/min (P < 0.025), and FENa from 0.67 +/- 0.15 to 1.24 +/- 0.28% (P < 0.025)., No significant changes in GFR or RPF were observed. Late proximal tubular-fluid-to-plasma (F/P) inulin decreased from 2.28 +/- 0.19 to a minimum value of 1.38 +/- 0.06 (P < 0.025). Absolute water reabsorption decreased from 15.8 +/- 3.5 to 6.5 +/- 1.7 nl/min (P < 0.025) and fractional water reabsorption from 52.0 +/- 4.4 to 26.5 +/- 4.1% (P < 0.025). The injection of 0.5 mumole of sodium vanadate (low dose) resulted in no significant changes in V. Late proximal F/P inulin decreased, however, from 2.37 +/- 0.14 to a minimum value of 1.59 +/- 0.12 (P < 0.025). SNGFR remained unchanged, as did GFR and RPF. UNaV increased from 1.41 +/- 0.35 to 2.25 +/- 0.35 microEq/min (P < 0.025), and FENa rose from 0.64 +/- 0.16 to 0.91 +/- 0.15% (P < 0.025). The decrease in F/P inulin was observed in all but one animal, even in the absence of a diuretic response. The amount of fluid remaining in the lumen of the late proximal tubule was virtually the same in both low- and high-dose animals (18.9 +/- 3.0 and 19.5 +/- 3.4 nl/min, respectively). We conclude that sodium vanadate causes a decrease in superficial proximal tubule fluid and salt reabsorption. Inasmuch as the low dose does not result necessarily in a diuretic response, an increase in fluid reabsorption distal to the late proximal tubule must take place.

Indacrinone: Modification of diuretic, uricosuric, and kaliuretic actions by amiloride

The response to indacrinone, a new indanone diuretic, was studied in 12 healthy subjects. Ten milligrams alone and in combination with either 2.5 mg or 5 mg amiloride was given in a randomized double-blind study with placebo control to study its action and to assess the optimum combination. Indacrinone alone induced an increase in urine flow rate and in sodium, potassium, and hydrogen ion excretion for at least 8 hr. Indacrinone also induced an initial uricosuria in the first 4 hr, followed by urate retention in the subsequent 12 to 24 hr, with no resultant change in the mean 24-hr urate excretion and minimal changes in the serum urate concentrations. The addition of 2.5 mg amiloride to the 10 mg indacrinone lowered potassium excretion to control levels, whereas addition of 5 mg amiloride resulted in net retention of potassium. With both doses of amiloride, the increased free hydrogen ion excretion after indacrinone returned to placebo levels. There were minor increases in serum creatinine, consistent with volume depletion due to the diuresis. There was a reduction in urinary calcium excretion. Our study shows that the combination of 10 mg indacrinone and 2.5 mg amiloride induces useful diuresis with minimal overall effect on urate, potassium, and hydrogen ion excretion.

Is urinary flow rate a major regulator of prostaglandin E excretion in man?

Urinary PGE 2 excretion is enhanced in several polyuric states in man suggesting that PGE 2 synthesis could be a mediator of diuresis. To explore the alternate hypothesis that polyuria is the cause of the increased PGE 2 excretion, we increased urine flow rate by intravenous administration of dextrose and water with different magnesium, calcium and potassium solutions in four normal males. Urinary PGE excretion rose in parallel with urine volume (r = 0.65 p < 0.01) independently of the electrolyte solution. To determine the effects of chronic alterations in water balance in 5 female subjects, we sequentially regulated oral water intake to induce 1, 2, 4 and 8 liters of urine volume/day. During low (40 mEq) sodium diets, PGE increased from 540 ± 50 to 4880 ± 1240 ng/d with increasing urinary volume (r = 0.81, p < 7.01). Similarly, for 200 mEq sodium intake PGE paralleled urinary volume (from 630 ± 100 to 4740 ± 800 ng/d, r = 0.61, p <0.01). In vitro sample dilution studies demonstrated no interference from method blank, and the addition of thin layer chromatography prior to Sephadex chromatography failed to alter assay measurements. We conclude that extreme increases in urinary flow rate may directly enhance PGE excretion in man.

Effects of alterations in urine flow rate on prostaglandin E excretion in conscious dogs.

The relationships between urinary prostaglandin E excretion and urine flow rate were evaluated in 11 conscious mongrel dogs during antidiuresis, maximal water loading, vasopressin administration during maximal water loading, and mannitol infusion. Urine flow rates between 0.21 and 15.1 ml/min were achieved. Urinary prostaglandin E excretion rates, determined by a membrane receptor assay, varied directly with urine flow rates (r = 0.908). Vasopressin administration (34--540 microU . kg-1 . min-1) resulted in a fall, rather than the expected rise, in urinary prostaglandin E excretion. When the concentration of prostaglandin E in the urine was plotted against urine flow rate, the demonstrated relationship appeared most consistent with passive diffusion. Mannitol infusion increased urine flow rates to levels comparable to the levels seen with maximal water loading but did not result in a fall in plasma osmolality. Urinary prostaglandin E excretion rates, however, were not distinguishable from those in the previous group. These data demonstrate that urinary prostaglandin E excretion rates are determined, to a great extent, by urine flow rate and that the significance of the interpretation of elevated excretion levels of these lipids in diuretic states may have to be reevaluated.

Ammoniagenesis by the isolated perfused rat kidney: the critical role of urinary acidification.

1. The effect of metabolic acidosis simulated in vitro on ammoniagenesis was investigated by using the isolated kidney of the rat perfused with an albumin Krebs-Henseleit medium containing glutamine and glucose. 2. Addition of HCl to a perfusate of normal bicarbonate concentration resulted in a prompt increase in urine flow rate, decrease in fractional sodium reabsorption and decrease in urine pH. 3. A minimum urine pH as low as 5.15 was achieved, with an average value of 5.92, indicating that this preparation has the capacity to acidify normally. 4. In contrast with studies in vitro with other preparations, with the functional perfused kidney a diminution in perfusate bicarbonate concentration resulted in a prompt increase in ammonia production, which was strikingly correlated with the decrease in urine pH. 5. The increase in ammonia production was diminished in studies carried out with a non-urinating kidney, in comparison with those that exhibited significant urine acidification. 6. These data suggest that a decrease in urine pH with trapping of ammonia in the urine may be a critical stimulus for increased ammonia production in acute metabolic acidosis.

Hypothalamic temperature and osmoregulation in the Pekin duck.

The temperature of the anterior and middle hypothalamus of conscious Pekin ducks was altered with chronically implanted thermodes. Both urine formation and salt secretion by the supraorbital glands were influenced by hypothalamic cooling. When osmotic diuresis was induced by continuous intravenous infusion of 1.2 ml . min-1 of 293 mosm . kg-1 mannitol in H2O solution, hypothalamic cooling increased urine flow rate at reduced urine osmolality and unchanged osmolal excretion rate. The degree of this cold induced diuresis increased with cooling intensity. Additional ADH administration by continuous infusion at a supramaximal dose abolished the diuretic effect of hypothalamic cooling. When water diuresis was induced by intragastric continuous infusion of 1.2 ml . min-1 of distilled water, hypothalamic cooling enhanced the diuresis, but hypothalamic warming had equivocal effects. The diuretic effects of hypothalamic cooling suggest an inhibition of endogeneous ADH release by lowering hypothalamic temperature. When the salt glands of salt adapted ducks were stimulated by continuous intravenous infusion of 0.2 ml . min-1 of 800 mosm . kg-1 NaCl in H2O solution, hypothalamic cooling reduced the salt gland secretion rate to an extent depending on cooling intensity. It is concluded that the activities of those integrative and/or efferent hypothalamic neurons, which mediate the hormonal control of renal water absorption and the nervous control of salt secretion by the supraorbital gland, depend on their own temperature.

Urine concentration dynamics in the postprandial and the fasting Myotis lucifugus lucifugus

1. 1. The postprandial bat initially increased urine flow rate and urine concentration and 7–9.5 hr later decreased urine flow rate while maintaining an elevated urine concentration. 2. 2. The fasting bat produced an increasingly concentrated urine at a uniform rate. 3. 3. The relationship of osmotic clearance to urine flow rate in the postprandial bat suggests an increase in glomerular filtration rate (GFR) in the bat kidney in response to food intake and a decrease in GFR when wastes have been removed. 4. 4. Alterations in GFR with feeding may aid this periodically feeding insectivore to minimize urinary water loss.

Renal histamine H1 and H2 receptors: characterization and functional significance.

Canine experiments were designed to determine if both histamine H1 and H2 receptors are present in the renal circulation. Renal blood flow (RBF) increased steeply over the first minute of intra-arterial histamine infusion, then increased gradually to a plateau in 3--5 min. Infusion of either histamine + H2 antagonist or of H1 agonist produced the initial rapid increase in RBF, whereas infusion of either histamine + H1 antagonist or of H2 antagonist produced a slower but more sustained increase in RBF. Histamine significantly increased urine flow rate (V), chloride excretion, and glomerular filtration rate (GFR). Infusion of the H2 agonist also increased V and Cl excretion without affecting GFR. By contrast H1 agonist significantly reduced V and Cl excretion and tended to reduce GFR (P less than 0.1 greater than 0.05). Histamine, H1 agonist, and H2 agonist each increased inner cortical more than outer cortical blood flow. These data suggest that 1) H1 and H2 receptors are present in the renal vasculature, 2) changes in intrarenal blood flow distribution are not responsible for histamine-induced diuresis, and 3) H1 receptors are primarily postglomerular while H2 receptors exhibit both pre- and postglomerular distribution.

Enflurane nephrotoxicity and pre-existing renal dysfunction.

This study provides the first morphological evidence of significant structural damage following high doses of enflurane alone and confirms previous findings of transient renal functional abnormalities following high dosage enflurane. The study also indicates that enflurane may have a greater potential for renal toxicity in the presence of renal impairment. Treatment of Fischer 344 rats with a nephrotoxic dose of gentamicin prior to six hours of enflurane (GE) anaesthesia at 1 MAC resulted in increased serum concentration of the enflurance metabolite inorganic fluoride (GE, 43.9 +/- 1.5; E, 34.5 +/- 1.8 mu mol/L), increased urine flow rate and a greater degree of structural damage in renal proximal convoluted tubule cells than was observed with either gentamicin (G) or enflurane (E) alone. Treatment with gentamicin prior to enflurane also resulted in reduced urinary osmolality compared to enflurane or gentamicin alone (GE, 742 +/- 57; E, 1709 +/- 66; G, 985 +/- 32 m0sm/kg).

Role of prostaglandis in the control of renin secretion in the dog (II)

Infusion of prostaglandin E 1 (PGE 1) into the renal artery of anesthetized dogs (1.03 μg/min) caused increases in urine flow rate (V), renal plasma flow (RPF) and renin secretion rate without any change in mean arterial blood pressure (MABP), whereas infusion of prostaglandin F 2α (PGF 2α), (1.03 μg/min) caused no consistent change in V, RPF, or renin secretion rate. Infusion of prostaglandin E 2 (PGE 2) (1.03 μg/min) into the renal artery of “non-filtering” kidneys caused renin secretion rate to rise from 567.7 ± 152.0 U/min(M ± SEM) during control periods to 1373.6 ± 358.5 U/min after 60 minutes of infusion of PGE 2 (P < 0.01), without significant change in MABP (P > 0.1). The data suggest that PGE 1 and PGE 2 play a role in the control of renin secretion. The data further suggest that PGE may control renin secretion through a direct effect on renin-secreting granular cells.

Urine catecholamine excretion after large doses of fentanyl, fentanyl and diazepam and fentanyl, diazepam and pancuronium.

The effects of fentanyl (0.5 mg/kg iv), fentanyl with diazepam (1 mg/kg iv) and fentanyl, diazepam and pancuronium (0.1 mg/kg iv) on heart rate (HR), mean arterial blood pressure (BP), cardiac output (QT), urine flow rate and urine epinephrine and norepinephrine excretion were determined in nine dogs. Fentanyl did not significantly change QT or BP but did reduce HR and urine flow rate (P less than 0.05). Urine epinephrine and norepinephrine excretion rates were signicantly increased by fentanyl (P less than 0.05). Diazepam caused no significant further changes in QT, BP or HR 30 minutes after administration, but urine epinephrine and norepinephrine excretion rates were reduced to control (pre-fentanyl) levels. Addition of pancuronium after fentanyl and diazepam increased urine flow rate to pre-fentanyl levels and elevated QT, BP and HR above controls but produced no significant change in urine epinephrine or norepinephrine excretion. These data suggest that fentanyl increases catecholamine blood levels and imply that the latter may be one mechanism by which cardiovascular dynamics are maintained stable during fentanyl anaesthesia. Our findings also demonstrate that cardiovascular stimulation after pancuronium is not associated with increased urinary catecholamine excretion.

THE ETIOLOGY OF METHOXYFLURANE NEPHROTOXICITY

COUSINS, M. J.; MAZZE, R. I.; KOSEK, J. C.; HITT, B. A.; LOVE, F. V. Author Information

Effect of angiotensin on glomerular filtration of albumin.

Angiotensin-induced proteinuria was examined at the glomerular-tubular level in rats. Ultra-micro-disc electrophoresis was employed to determine albumin concentration of rat proximal tubular fluid samples under control conditions and during the infusion of 0.15 mug/min X 100 g body weight angiotensin II using micropuncture techniques. Under control conditions proximal tubular albumin concentration was 1.32 +/- 0.79 (SD) mg/100 ml (n = 71). There was no correlation between albumin concentration and (TF/P)-inulin ratio indicating an albumin reabsorption in the proximal tubule parallel to fluid reabsorption under control conditions. During angiotensin infusion using re-collection techniques, there is an average increase of 26 times in tubular albumin concentration, indicating an increase in albumin filtered. There was no change in GFR, SNGFR, transit time, (TF/P)-inulin ratio, an increase in urine flow rate, sodium excretion, protein excretion, mean arterial blood pressure during angiotensin infusion. Since effective glomerular filtration pressure was not increased during angiotensin it is concluded that angiotensin-induced proteinuria is due to an increase in filtered protien mediated by a change in glomerular permeability to proteins.

Diuretics in chronic renal disease: a study of high dosage frusemide.

1. The efficacy and mode of action of frusemide (100–750 mg) have been studied acutely in thirty-four investigations on twenty-four water-loaded subjects with stable, non-oedematous chronic renal disease (GFR 2.3–26.0 ml/min) of varying aetiology (fourteen ‘tubular’, ten ‘glomerular’). 2. Water loading alone resulted in a slight increase in urine flow rate, a flow-dependent rise in electrolyte excretion and a small fall in urine osmolality. 3. Basal fractional excretion of fluid and electrolytes was closely related to GFR, increasing as this fell, so that at a GFR of 3.0 ml/min 80% of the fluid filtered, 50–60% of the filtered load of sodium and chloride and 400% of potassium was excreted. 4. After oral or intravenous frusemide, up to 93% of the filtered load of chloride, 87% of sodium and apparently all of the glomerular filtrate could be excreted; the magnitude of the response depended on dose, GFR and basal fractional sodium excretion, being greatest at higher GFR and lowest fractional excretion. Free water clearance increased. 5. No significant change in inulin clearance was found after frusemide and no difference in the response of ‘tubular’ as opposed to ‘glomerular’ subjects. 6. Long-term treatment of nineteen patients with ‘resistant’ oedema and chronic renal disease has shown high dosage frusemide (0.12–2.0 g/day) to be an effective diuretic, although significant side effects were found in five patients.

Natriuresis after occlusion of the hepatic artery and portal vein

The renal response to an isotonic saline load was studied in dogs with a side-to-side superior mesenteric-caval shunt before and after hepatic inflow occlusion to determine if the liver influenced renal sodium excretion. During the control period, there was no difference between the eight sham-operated and eight experimental dogs. During the study period, the sham dogs, who only had manipulation of the hepatic artery and portal vein, had an increased urine flow rate and renal sodium excretion, while the experimental dogs with hepatic inflow occlusion had a statistically-in-significant decrease in renal sodium excretion. The change in filtered sodium from control to study periods was unrelated to the change in sodium excretion in the sham dogs but was directly related in the experimental dogs. When the difference from control to study periods was compared in sham and experimental dogs, there was a significant difference for urine flow rate, and fractional and total renal sodium excretion. Absence of the liver appears to influence renal sodium excretion and may be of significance for sodium retention with liver disease.