Transfer of Electrolytes Across the Urinary Bladder in the Dog

Hlad, C. J.; Nelson, Robert L.; Holmes, Joseph H.

doi:10.1152/ajplegacy.1956.184.2.406

Cited by 28 publications

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“…For example, although high protein diets increase urinary urea excretion, they also decrease urinary pH while increasing urinary ammonium, net acid, phosphorous, and calcium excretion (2). Because Hlad and coworkers (15) showed that low urinary pH increases transport of urinary sodium and chloride (they did not study urea) across dog bladder in vivo and because recent work in sheep rumen epithelium has demonstrated a lumenal pH modification of urea transport, likely by affecting UT-B (1), we cannot rule out an effect of urine pH on urothelial permeability. In addition, we cannot rule out an independent bladder or urothelial factor(s), also dependent on dietary protein intake, possibly affecting urothelial urea reabsorption.…”

Section: Discussionmentioning

confidence: 99%

“…Spector and coworkers (39) described high concentrations of urea (and creatinine) in both rat and dog bladder tissues; in rats, water deprivation increased tissue urea concentrations whereas water loading decreased tissue urea concentrations, suggesting that animal hydration status might regulate the magnitude of urothelial transport. Furthermore, several older in vivo studies have demonstrated net vectoral transport of water, ions, and solutes across epithelial membranes, usually down their concentration gradients, in several mammalial species (15,16,23,31,33,44,45,46). Levinsky and Berliner (23) reported loss of water, potassium, osmoles, and up to 20% of urea from "artificial urine" in slowly perfused dog ureter and bladder, and Walser et al (45) noted net loss of potassium, creatinine, and 7% of urea from urine perfusing ureters over 3 min duration in moderately dehydrated rats.…”

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confidence: 99%

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Dietary protein affects urea transport across rat urothelia

Spector

Deng

Stewart

2012

American Journal of Physiology-Renal Physiology

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Spector DA, Deng J, Stewart KJ. Dietary protein affects urea transport across rat urothelia. Am J Physiol Renal Physiol 303: F944-F953, 2012. First published July 25, 2012 doi:10.1152/ajprenal.00238.2012.-Recent evidence suggests that regulated solute transport occurs across mammalian lower urinary tract epithelia (urothelia). To study the effects of dietary protein on net urothelial transport of urea, creatinine, and water, we used an in vivo rat bladder model designed to mimic physiological conditions. We placed groups of rats on 3-wk diets differing only by protein content (40,18,6, and 2%) and instilled 0.3 ml of collected urine in the isolated bladder of anesthetized rats. After 1 h dwell, retrieved urine volumes were unchanged, but mean urea nitrogen (UN) and creatinine concentrations fell 17 and 4%, respectively, indicating transurothelial urea and creatinine reabsorption. The fall in UN (but not creatinine) concentration was greatest in high protein (40%) rats, 584 mg/dl, and progressively less in rats receiving lower protein content: 18% diet, 224 mg/dl; 6% diet, 135 mg/dl; and 2% diet, 87 mg/dl. The quantity of urea reabsorbed was directly related to a urine factor, likely the concentration of urea in the instilled urine. In contrast, the percentage of instilled urea reabsorbed was greater in the two dietary groups receiving the lowest protein (26 and 23%) than in those receiving higher protein (11 and 9%), suggesting the possibility that a bladder/urothelial factor, also affected by dietary protein, may have altered bladder permeability. These findings demonstrate significant regulated urea transport across the urothelium, resulting in alteration of urine excreted by the kidneys, and add to the growing evidence that the lower urinary tract may play an unappreciated role in mammalian solute homeostasis.solute transport across bladder epithelia; urothelial creatinine transport; regulation of urothelial urea transport ALTHOUGH MAMMALIAN LOWER URINARY tract functions primarily as a short-term transit and storage vehicle for urine made by the kidneys (13), recent data demonstrate that mammalian urothelia (the epithelial cell lining of the urinary tract from renal pelvis to proximal urethra) is a surprisingly dynamic and complex tissue that may play an unappreciated role in water and solute homeostasis (35)(36)(37)(38)(39) reviewed in Ref. 22). While the urothelial permeability barriers, thought to reside in the apical membrane of the large "umbrella" cells lining the urinary tract lumens, the tight junction (TJ) between those cells, and the adherent overlying urinary glycosaminoglycans (GAG) layer (18,19,22,24,48), have been shown in vitro to have low permeability to water, urea, and ions (9,25,28), there are a number of physiological factors that might be expected to promote (even) passive diffusion of water and solutes across these barriers, including the large urinary tract lumenal surface area, long storage time of urine, enormous and changing concentration gradients for water, solutes, and ions, and ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Dietary protein affects urea transport across rat urothelia

Spector

Deng

Stewart

2012

American Journal of Physiology-Renal Physiology

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“…Previous studies that examined net in vivo potassium flux in bladder and ureter have demonstrated potassium reabsorption down its concentration gradient from lumen (urine or artificial test solutions) to blood (8,16,27,34). Although the mechanism(s) of potassium reabsorption may, in part, be secondary to passive diffusion and or leak across the apical cell membrane or through tight junctions, in recent electrophysiological studies, Sun and coworkers (33) showed a strongly rectifying potassium current with conductive characteristics of the K ir 2.1 channel as well as the Maxi-K channel in normal cultured human bladder cells (33), and, in Ussing chamber experiments with rabbit bladder, Wang et al (35) demonstrated that increased mucosal hydraulic pressure led to increased sodium reabsorption (probably through ENaC) as well as potassium secretion, likely through a stretch-activated nonselective cation channel.…”

Section: Discussionmentioning

confidence: 99%

“…In these experiments, fluxes usually occurred in the direction of the concentration gradient, but fluxes were influenced as well by urine pH (8), bladder volume (9), and hydrostatic pressure (35).…”

mentioning

confidence: 91%

The ROMK potassium channel is present in mammalian urinary tract epithelia and muscle

Spector¹,

Yang²,

Klopouh³

et al. 2008

American Journal of Physiology-Renal Physiology

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There is increasing evidence that mammalian urinary tract epithelial cells utilize membrane channels and transporters to transport solutes across their apical (luminal) and basalateral membranes to modify solute concentrations in both cell and urine. This study investigates the expression, localization, and regulation of the ROMK (Kir 1.1) potassium channels in rat and dog ureter and bladder tissues. Immunoblots of homogenates of whole ureter, whole bladder, bladder epithelial cells, and bladder smooth muscle tissues in both rat and dog identified ϳ45-to 50-kDa bands characteristic of ROMK in all tissues. RT-PCR identified ROMK mRNA in these same tissues in both animal species. ROMK protein localized by immunocytochemistry was strongly expressed in the apical membranes of the large umbrella cells lining the bladder lumen and to a lesser extent in the cytoplasm of epithelial cells and smooth muscle cells in the rat bladder. ROMK protein and mRNA were also discovered in cardiac, striated, and smooth muscle in diverse organs. There was no difference in immunoblot expression of ROMK abundance in bladder homogenates (whole bladder, epithelial cell, or muscle cell) or ureteral homogenates between groups of rats fed high-or low-potassium diets. Although the functional role of ROMK in urinary tract epithelia and smooth muscle is unknown, ROMK may participate in the regulation of epithelial and smooth muscle cell volume and osmolality, in the dissipation of potassium leaked or diffused from urine across the epithelial cell apical membranes or tight junctions, and in net or bidirectional potassium transport across urinary tract epithelia. epithelial sodium channel; calponin MAMMALIAN URINARY TRACT EPITHELIA (urothelia) has long been held to serve solely as a storage conduct for urine made by the kidney and, in particular, to prevent modification of urine by inhibiting net flux of water and solutes across the epithelial cell luminal membrane (7). The barrier(s) preventing transepithelial flux of urine constituents have been shown to include: the lumenal membrane (containing unique uroplakin proteins) of the large ("umbrella") cells lining the urinary tract lumen (12), tight junctions adjoining the umbrella cells, and a glycosaminoglycans layer overlying and adjacent to the lumenal membrane (13, reviewed in Ref. 17). Evidence for the effectiveness of these barriers, which have been thought to be passive in nature and not to utilize or require membrane transporters, comes from Ussing chamber studies documenting very low urothelial permeability to water, ions, and nonelectrolytes and very high transepithelial cell resistance in stretched bladders and apical membrane endosomes obtained from rabbits under basal conditions (2, 24).However, although the permeabilities of urothelia for water and various urinary solutes may be low under basal conditions, urothelial permeabilities in animals subjected to dietary, physiological (e.g., water loading/water restricted), or other stress could be altered. Furthermore, urothelial cells are...

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“…Previous work has shown that the urinary bladders of rabbits, dogs and humans are slightly permeable to inorganic ions such as I, Na+, Cl-, K+, H+, Br-and PO'- (Read & Care, 1954;Maluf, 1955;Englund, 1956;Hlad, Nelson & Holmes, 1956;Andrysek & Schuck, 1959;Rapoport, Nicholson & Yendt, 1960). Organic molecules such as glycine, glucose and tryptophan and some of its metabolites are extensively reabsorbed from the urinary bladder of the mouse within 24h of administration (Bryan, Morris & Brown, 1965;Morris & Bryan, 1966).…”

Section: Introductionmentioning

confidence: 99%

RAPID ABSORPTION FROM THE URINARY BLADDER OF A SERIES OF n‐ALKYL CARBAMATES: A ROUTE FOR THE RECIRCULATION OF DRUGS

Bridges

Sargent

Upshall³

1979

British J Pharmacology

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I The rate of loss of a series of n-alkyl carbamates from the lumen of the urinary bladders of female rats has been studied. 2 The rate of loss obeys first order kinetics and was not affected by water flux across the bladder wall nor by binding of the carbamates to it. 3 The rate of loss of octyl carbamate was reduced by about 76% by the presence of 5% Tween 80. Histological evidence indicates that this may be due to the formation of a thin luminal lining which may be adsorbed Tween 80 or mucopolysaccharide material. 4 The absorption rate of the carbamates was limited by their hydrophilicity but reached a plateau for the more lipophilic homologues with a half life for loss of approximately 10 min. 5 The implications of these results with regard to the recirculation of unmetabolized drugs and hydrolysed conjugates of drugs, the systemic absorption of intravesically applied cancer chemotherapeutic agents and bladder wall permeability to carcinogens are discussed.

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Transfer of Electrolytes Across the Urinary Bladder in the Dog

Cited by 28 publications

References 0 publications

Dietary protein affects urea transport across rat urothelia

Dietary protein affects urea transport across rat urothelia

The ROMK potassium channel is present in mammalian urinary tract epithelia and muscle

RAPID ABSORPTION FROM THE URINARY BLADDER OF A SERIES OF n‐ALKYL CARBAMATES: A ROUTE FOR THE RECIRCULATION OF DRUGS

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