UMLS:C0403608 - FACTA Search

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Query: UMLS:C0403608 (ureter)
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In previous reports from this laboratory we have suggested that a reduction in medullary tonicity decreases the thin ascending loop of Henle sodium reabsorption and is in part responsible for the magnitude for the natriuresis accompanying 10% body weight Ringer loading. According to this postulate, one would expect that the medullary washout associated with water diuresis would also result in a natriuresis, but this does not occur. It is possible, however, that increased delivery from the proximal tubule is necessary to demonstrate an effect of medullary tonicity on urinary sodium excretion. Micropuncture studies were designed to test that possibility by increasing distal delivery by 2% Ringer loading in animals with and without reduced medullary tonicity. In an initial series of experiments the alpha-adrenergic agonist clonidine was used to induce a water diuresis. When given alone, this agent caused a marked decrease in urine osmolality and an increase in urine flow rate but had no effect on proximal reabsorption in either superficial or juxtamedullary nephrons, and did not alter urinary sodium excretion. Volume expansion with 2% body weight Ringer solution resulted in a significant fall in proximal reabsorption and a trivial increment in sodium excretion. When this same degree of volume expansion was conferred on animals undergoing a water diuresis, a marked increase in absolute and fractional sodium excretion occurred. In a second group of studies medullary tonicity was reduced in the left kidney only by removal of the left ureter 1 h before micropuncture. When these animals were infused with 2% body weight Ringer solution, proximal reabsorption was decreased in juxtamedullary nephrons, and a marked increase in sodium excretion was observed only from the left kidney. Finally, the effect of water diuresis on fractional sodium delivery to the early and late distal tubule of superficial nephrons during 2% Ringer loading was evaluated. Delivery to both of these sites was comparable after 2% Ringer loading alone and during 2% Ringer loading plus water diuresis. From these data, we conclude that medullary tonicity does influence renal sodium handling but that this effect is manifest in the final urine only under conditions in which proximal reabsorption is decreased. The data also suggest that this effect is limited to juxtamedullary nephrons and is probably localized to the thin ascending limb of the loop of Henle.
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PMID:Effect of medullary tonicity on urinary sodium excretion in the rat. 707 54

Kidney function has been studied in pig fetuses (105-109 d of gestation) and neonates (5-7 d old). Urine was collected by catheterization of the ureter. Inulin clearance, the excretion of electrolytes and the osmolality of urine and plasma were measured. In addition the response of the fetal neurohypophysis and fetal and neonatal kidney to a reduction of plasma osmolality was studied. The results show that the inulin clearance increases rapidly in the perinatal period, at a rate greater than would be expected from the gain in body weight. The re-absorption of Na and K is well developed. The fractional sodium excretion in fetuses is 2% and is 0.1% in the new-borns. The urine osmolality is high, probably due to high plasma lysine vasopressin levels persisting throughout the experiment. The infusion of hypotonic saline results in a significant decrease of plasma osmolality but only three out of nineteen animals showed an increase in urine flow. Although lysine vasopressin concentrations fell in some animals the urine stayed hyperosmotic as compared with plasma. The results show that fetuses and neonates may react to volume load but in the conditions of these experiments that regulation of plasma osmolality was inadequate.
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PMID:Renal response to hypotonic saline load in fetal and new-born pigs. 707 46

Partial obstruction of the left ureter was created in seven dogs. Renal function was studied 3 weeks later. Total renal blood flow (RBF) and intrarenal blood flow distribution were studied using the microsphere technique. Glomerular filtration rate (GFR), effective renal plasma flow (CPAH) and the excretion of sodium and osmolar substances were determined using the clearance technique. RBF, GFR and CPAH in the hydronephrotic kidney were reduced to approximately 30% of the same parameters in the contralateral kidney. Urinary sodium excretion was consistently lower in the hydronephrotic than in the contralateral kidney. Volume expansion with isotonic saline solution revealed that this reduction of sodium excretion from the hydronephrotic kidney was out of proportion to the extent of GFR reduction. The contralateral unobstructed kidney did not compensate for this salt retention by increasing its sodium excretion.
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PMID:Renal function in dogs with chronic moderate unilateral ureteral obstruction. 713 86

Experiments were carried out on smooth muscle cells (SMC) of the guinea-pig ureter by the double sucrose gap method with simultaneous recording of electrical and contractile activities. The effect of histamine on SMC was studied in normal Krebs solution and in sodium-free Krebs solution with TEA. In normal Krebs solution, histamine was shown to increase the duration of AP plateau and contraction. In sodium-free Krebs solution with TEA, the APs of ureter SMC also had a plateau that was determined by the increased calcium conduction of the membrane. In these conditions, histamine provoked a decrease in the duration of the AP plateau and contraction. The histamine effect was blocked by phencarol both in normal and sodium-free Krebs solution with TEA. A possible role of sodium, calcium and potassium ions in the modulating action of histamine on excitation of ureter SMC is discussed.
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PMID:[Mechanism of modulating effect of histamine on the excitation and contraction of smooth muscles of the ureter]. 717 28

In 2 separate series of dogs a segment of ureter was isolated from both bladder and kidney and left in situ with an intact blood supply. Tense cysts formed in these sequestered segments regardless of whether the ends were occluded or the segments were split longitudinally and left open. The formation of these cysts can be prevented by the removal of the urothelium. The cyst contents were found consistently to have a sodium concentration below that of the simultaneously obtained serum concentration and urea concentration higher than the simultaneously obtained serum urea. Osmolalities and protein levels within the cysts were virtually identical to the serum levels.
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PMID:Sequestration of ureteric segments in dogs. 723 40

The effect of different albumin concentrations on whole kidney function has been studied in the isolated perfused rat kidney. When a dialyzer was included in the perfusion circuit, GFR and sodium transport remained nearly constant for 2 h. Perfusion flow rate was directly correlated with albumin concentration. GFR was low (0.56 ml.min-1.g-1) at high albumin concentration (7.6 g/100 ml) and highest (1.38 ml.min-1.g-1) when albumin was omitted. The latter observation differed from earlier findings by other investigators who found a reduced GFR in the absence of albumin. This reduced GFR could be explained by ureteral backpressure, which results from the use of narrow ureter catheters. Fractional sodium reabsorption was approximately 50% irrespective of load when albumin was absent, and reached 90% at a GFR of 0.95 ml.min-1.g-1 when 5-6 g/100 ml albumin was used. At reduced load, fractional sodium reabsorption approached in vivo values of 98%. Potassium secretion was observed at high urinary flow rates when albumin concentration was low; low urinary flow rates at high protein concentration were associated with net potassium reabsorption.
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PMID:Effect of albumin on the function of perfused rat kidney. 724 41

In ureter-ligated rats, the pressor effects of both norepinephrine and angiotensin II i.v. on systemic blood pressure and serum sodium concentration were significantly decreased when compared with those in control rats, while serum potassium concentration, blood urea nitrogen, mean systemic blood pressure and plasma renin activity were significantly increased. The microscopic examination of aortic smooth muscles did not show significant histological lesions in the tissues obtained from ureter-ligated rat. The responsiveness of aortic strips isolated from ureter-ligated rats to norepinephrine and angiotensin II was significantly decreased in comparison with that from control rats. The results suggest that a decreased pressor response to norepinephrine and angiotensin II under ureter-ligated conditions may be attributed to a decrease in vascular reactivity to drugs.
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PMID:Changes in vascular reactivity in rats with experimental renal insufficiency. 732 63

The luminal membrane of collecting duct cells, especially the intercalated cells, is normally exposed to active kallikrein. This is the consequence of the specific localization of this renal enzyme in the connecting tubule cells and its principal route of secretion being into the tubular lumen. It is conceivable that kallikrein acts downstream on a transporter involved in distal bicarbonate handling. To investigate this possibility, we estimated bicarbonate concentration and measured kallikrein amidolytic activity in urine fractions collected after a classical stop-flow experiment in rabbits. A highly significant inverse correlation was found between these parameters (r = -0.94, p < 0.001) in the peak kallikrein fractions. Neither sodium nor potassium concentration were correlated to kallikrein. This suggests that the physiological role of renal kallikrein may be to regulate extracellular fluid pH by inhibiting collecting duct bicarbonate secretion. To test the hypothesis that tubular fluid kallikrein activity and bicarbonate secretion are causally related, we developed a novel in vivo stop-flow injection model ('orthograde stop-flow'). A hog-kallikrein containing solution (0.5 microgram/ml) was injected through the abdominal aorta into the renal tubular system of one kidney of barbiturate-anesthetized rats, while the renal blood supply was interrupted. The ureter was then occluded and renal blood perfusion reinitiated. After a 2-min contact time five 125-microliters urine fractions were collected. Bicarbonate secretion was clearly detected in the second and third fractions (i.e. those coming from the collecting ducts) of the control animals, which had received only the vehicle. There was no bicarbonate secretion peak in the corresponding urine fractions collected from kallikrein-injected animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evidence for an inhibitory effect of kallikrein on collecting duct bicarbonate secretion in rats and rabbits. 753 9

The mechanisms that mediate the actions of bradykinin on ureteral motility are poorly defined and mediation via prostaglandins has not been examined. Therefore, the effects of bradykinin on contractility and the possible mediator role of prostaglandins have been investigated in sheep ureter. At the concentrations of 10(-8), 10(-7) and 10(-6) M, bradykinin elicited marked reductions in contractile force. When ureteral strips were treated separately with 10(-6) M indomethacin, 2 x 10(-6) M sodium salicylate and 10(-5) M aspirin, each drug produced a significant decrease in contractile force. In strips in which prostaglandin synthesis was inhibited by the above concentrations of indomethacin, sodium salicylate and aspirin, 10(-7) M bradykinin significantly decreased the contractility. From these data, we concluded that in ureter bradykinin decreases contractility via a mechanism not involving prostaglandin generation.
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PMID:Prostaglandin-independent decrease of sheep ureter contractility induced by bradykinin. 753 18

1. We have investigated the effect of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase inhibitor, cyclopiazonic acid (CPA), on electromechanical coupling in the guinea-pig ureter. All experiments were performed in capsaicin-pretreated (10 microM for 15 min) ureters to prevent the release of sensory neuropeptides from afferent nerves. 2. In organ bath experiments, electrical field stimulation (EFS, 10 Hz for 1 s, 5 ms pulse width, 60 V) produced tetrodotoxin- (1 microM) resistant phasic contractions which were enhanced by Bay K 8644 (1 microM) and abolished by nifedipine (10-30 microM). 3. CPA (10 microM) enhanced the EFS-evoked contractions both in the absence and presence of Bay K 8644. The effect of CPA was concentration-dependent between 1 and 30 microM. The response to 10 microM CPA was biphasic: the maximal enhancement (58 +/- 3% increase) was observed within 10-20 min from CPA administration, followed by a decline to a new steady state (25 +/- 5% increase over baseline) at 50-60 min. The effect of CPA was reversed by washout. 4. Ryanodine (100 microM) produced a prompt enhancement of the EFS-evoked contractions of the guinea-pig ureter, which peaked at 42 +/- 3% increase over baseline; the co-administration of CPA (10 microM) and ryanodine (100 microM) produced a peak effect (60 +/- 8% enhancement) which was not different from that produced by CPA alone. With either ryanodine alone or ryanodine plus CPA, the enhancement of the EFS-induced contractions was biphasic, showing a time-course similar to that observed with CPA alone. Tetraethylammonium (10 mM) produced a significantly larger effect (93 +/- 13% increase over baseline) and its effect was sustained throughout the 60 min observation period. 5. In the presence of Bay K 8644, superfusion for 30 min with a low Na+ medium (60% of extracellular Na+ replaced by Li+ or choline) reduced the amplitude of EFS-evoked contractions by 20-35%. In both Li(+)- and choline-substituted media, spontaneous activity developed during superfusion with low Na+ Krebs solution which was suppressed by 10 microM nifedipine. CPA (10 microM) produced a marked enhancement of the EFS-evoked contractions in low-Na+ medium (both Li(+)- and choline-substituted) and this effect was sustained throughout the 60 min observation period. 6. In the absence of Bay K 8644, the response of the ureter smooth muscle to EFS is characterized by a refractory period: an interval of about 30 s was required between two applied stimuli to produce a second response comparable in size to that elicited by the first stimulus. CPA (10 micro M, 10-20 min before)markedly reduced the refractory period of the guinea-pig ureter to EFS.7. CPA (10 micro M, 30-60 min before) increased the phasic component of contraction produced by 80 m MKCl. The tonic component of the response to KCl was slightly but not significantly reduced by CPA,and a 'hump' in the tonic contraction was observed at 1-2 min from addition of KCl.8. In sucrose gap experiments, 10 micro M CPA produced a sustained depolarization of the membrane and reduced the latency between application of electrical stimuli and onset of the action potential; these effects were maintained throughout the 60 min superfusion with CPA. CPA also transiently prolonged the plateau phase of the action potential and increased the peak amplitude of contraction: these effects peaked at about 10-20 min from start of superfusion with CPA and then declined. At the peak of its enhancing effect on contraction amplitude, CPA prolonged the contractile phase of the contraction relaxation cycle.9.Superfusion with a low-Na, choline-substituted Krebs solution produced a reversible membrane depolarization. In the presence of Bay K 8644 (1 micro M), action potentials and phasic contractions were superimposed on this depolarization which were abolished by nifedipine (1O micro M).10. These findings indicate that CPA augments the excitability and affects the contraction-relaxation cycle of the smooth muscle of the guinea-pig ureter, implying a role for sarcoplasmic reticulum Ca2+-ATPase in the regulation of electromechanical coupling. The effects of CPA resemble those produced by ryanodine and the effect of the two agents on the amplitude of contractions is non-additive.It appears that following blockade of the CPA-sensitive SR Ca2+ pump, other mechanism(s) may come into action to reduce intracellular Ca2+. The Na+/Ca2+ exchanger could be involved in the compensatory changes responsible for the fading of the response to CPA.
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PMID:Effect of the Ca(2+)-ATPase inhibitor, cyclopiazonic acid, on electromechanical coupling in the guinea-pig ureter. 753 95

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