Regulation of Na+ channel density at the apical surface of rabbit urinary bladder epithelium

Burton, Timothy J.; Edwardson, J. Michael; Ingham, Jamie; Tempest, Heidi; Ferguson, D. R.

doi:10.1016/s0014-2999(02)01912-x

Cited by 13 publications

(9 citation statements)

References 31 publications

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“…; Burton et al. ; Grasso and Calderon , ; Khandelwal et al. ) and Grasso has described endosomal release of fluid contents into cytosol (Grasso and Calderon ).…”

Section: Discussionmentioning

confidence: 99%

“…Given that hypertonicity also stimulates apical membrane endocytosis (Apodaca ; Burton et al. ), it is interesting that Minsky and Chlapowski reported a “striking positive correlation” in both contracted and dilated bladders between the size and number of subapical cytoplasmic vesicles and the osmolality of urine (Minsky and Chlapowski ).…”

Section: Discussionmentioning

confidence: 99%

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The urothelium of a hibernator: the American black bear

et al. 2015

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The American black bear undergoes a 3–5 month winter hibernation during which time bears do not eat, drink, defecate, or urinate. During hibernation renal function (GFR) is 16–50% of normal but urine is reabsorbed across the urinary bladder (UB) urothelium thus enabling metabolic recycling of all urinary constituents. To elucidate the mechanism(s) whereby urine is reabsorbed, we examined the UBs of five nonhibernating wild bears using light, electron (EM), and confocal immunofluorescent (IF) microscopy–concentrating on two components of the urothelial permeability barrier – the umbrella cell apical membranes and tight junctions (TJ). Bear UB has the same tissue layers (serosa, muscularis, lamina propria, urothelia) and its urothelia has the same cell layers (basal, intermediate, umbrella cells) as other mammalians. By EM, the bear apical membrane demonstrated a typical mammalian scalloped appearance with hinge and plaque regions – the latter containing an asymmetric trilaminar membrane and, on IF, uroplakins Ia, IIIa, and IIIb. The umbrella cell TJs appeared similar to those in other mammals and also contained TJ proteins occludin and claudin - 4, and not claudin –2. Thus, we were unable to demonstrate urothelial apical membrane or TJ differences between active black bears and other mammals. Expression and localization of UT-B, AQP-1 and -3, and Na+, K+-ATPase on bear urothelial membranes was similar to that of other mammals. Similar studies of urothelia of hibernating bears, including evaluation of the apical membrane lipid bilayer and GAGs layer are warranted to elucidate the mechanism(s) whereby hibernating bears reabsorb their daily urine output and thus ensure successful hibernation.

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“…; Burton et al. ; Grasso and Calderon , ; Khandelwal et al. ) and Grasso has described endosomal release of fluid contents into cytosol (Grasso and Calderon ).…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The urothelium of a hibernator: the American black bear

et al. 2015

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“…One possible mechanism might be reabsorption of urinary constituents during endocytosis of apical membranes. It is known that, particularly during bladder stretch and relaxation (filling and emptying) and during alternations of serosal and mucosal osmolality (8,9,43), there is an active and extensive simultaneous exocytosis and endocytosis cycling of membrane components (including uroplakins) between the apical cell membrane and numerous membrane-containing subapical discoidal or fusiform-shaped vesicles. Such cycling apparently contributes both to changing bladder surface area requirements during bladder stretch and relaxation cycles and to newly described sensory and effector functions of the urothelial cells (reviewed in Ref.…”

Section: Discussionmentioning

confidence: 99%

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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“…Expression of ENaC is plastic and is increased in human bladders with outlet obstruction . In addition there is active endocytotic and exocytotic traffic at the apical membrane of urothelial cells and the serosal face.…”

Section: Introductionmentioning

confidence: 99%

The regulation of ATP release from the urothelium by adenosine and transepithelial potential

et al. 2012

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What's known on the subject? and What does the study add?• Stretch of the urothelium, as occurs during bladder filling, is associated with a release of ATP that is postulated to act as a sensory neurotransmitter. The regulation of ATP release is poorly understood and in particular if there is a feedback mechanism provided by ATP itself.• Adenosine, a breakdown product of ATP, is a potent inhibitor of stretch-induced ATP release, acting through and A1 receptor; endogenous levels are about 0.6mM . Data are consistent with ATP release relying on the rise of intracellular Ca2+. Transepithelial potential also controls ATP release, also acting via an A1 receptor-dependent pathway. Objectives• To test the hypothesis that distension-induced ATP release from the bladder urothelium is regulated by adenosine as well as changes to transurothelial potential (TEP).• To examine the role of changes to intracellular [Ca 2+ ] in ATP release. Materials and Methods• Rabbit urothelium/suburothelium membranes were used in an Ussing chamber system. Distension was induced by fluid removal from the chamber bathing the serosal (basolateral) membrane face.• The TEP and short-circuit current were measured. ATP was measured in samples aspirated from the serosal chamber by a luciferin-luciferase assay. • Intracellular [Ca 2+ ] was measured in isolated urothelial cells using the fluorochrome Fura-2. All experiments were performed at 37°C. Results• Distension-induced ATP release was decreased by adenosine (1-10 mM) and enhanced by adenosine deaminase and A1-(but not A2-) receptor antagonists.• Distension-induced ATP release was reduced by 2-APB, nifedipine and capsazepine; capsaicin induced ATP release in the absence of distension.• ATP and capsaicin, but not adenosine, generated intracellular Ca 2+ transients; adenosine did not affect the ATP-generated Ca 2+ transient.• ATP release was dependent on a finite transepithelial potential. Changes to TEP, in the absence of distension, generated ATP release that was in turn reduced by adenosine. Conclusion• Adenosine exerts a powerful negative feedback control of ATP release from the urothelium via A1 receptor activation.• Distension-induced ATP release may be mediated by a rise of the intracellular [Ca 2+ ].• Modulation of distension-induced ATP release by adenosine and TEP may have a common pathway.

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Regulation of Na+ channel density at the apical surface of rabbit urinary bladder epithelium

Cited by 13 publications

References 31 publications

The urothelium of a hibernator: the American black bear

The urothelium of a hibernator: the American black bear

Dietary protein affects urea transport across rat urothelia

The regulation of ATP release from the urothelium by adenosine and transepithelial potential

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