1,721,034 research outputs found
Conventional and confocal epi-reflection and fluorescence microscopy of the rat kidney in vivo
No full textTo visualize superficial and accessible renal tubule cells functioning in situ and to relate what we can 'see' to what we know of their function from more invasive in vivo or less direct in vitro studies means applying and adapting recent advances in epifluorescence and confocal microscopy to improve image resolution and to combine this with the use of fluorescent labels to monitor the handling of specific molecules by the proximal and distal renal tubule cells in vivo. Doing this in living tissue is novel, especially in the kidney. Application of confocal microscopy to the imaging of living tissue, as opposed to isolated cells, has not been widely reported. The kidney surface has been imaged before using the confocal microscope and in preliminary studies we have extended this by using a different confocal system with and without fluorescence. While the studies published up to now have been morphological, comparing standard renal (structural) histology of surface glomeruli and renal tubules with the corresponding in vivo confocal images, more dynamic, real-time studies have been limited. Individual red blood cells can be seen flowing around the peritubule capillary network and nucleated white blood cells can also be distinguished. Tubule cells, endothelial cells, the proximal tubule cell brush border and cell mitochondria can be visualized. Filtration and secretion can be observed, and the early and late parts of the proximal tubule distinguished, and the distal tubule recognized. Localization of fluorescently labeled insulin to the luminal brush border and progressive uptake of label and distribution within proximal tubule cells toward the basolateral (blood side) membrane can be demonstrated. The possibility of monitoring hemodynamic changes and tracking the filtration, uptake, secretion and absorption of fluorescently tagged molecules, as well as intracellular fluorescence, e.g. calcium or pH is an exciting prospect and is ripe for detailed exploration
Urinary acidification and distal renal tubular acidosis
No full textHistorically, renal tubular acidosis (RTA) has been classified on a clinical basis, without any reference to the underlying disorder. Here we review the normal mechanisms of renal acidification and we identify disorders of specific transporters (genetic, disease-related or drug-induced) that lead to the main categories of distal RTA. We also describe the approach to diagnosis and the current treatment of distal RTA
Hormonal influences on renal tubule transport: glucagon, somatostatin,insulin, glucocorticoid, and thyroid hormones, catecholamines and selected gut-renal peptides
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Renal tubular acidosis: Developments in our understanding of the molecular basis
No full textRenal tubular acidosis is a metabolic acidosis due to impaired acid excretion by the kidney. Hyperchloraemic acidosis with a normal anion gap and normal (or near normal) glomerular filtration rate, and in the absence of diarrhoea, defines this disorder. However, systemic acidosis is not always evident and renal tubular acidosis can present with hypokalaemia, medullary nephrocalcinosis and recurrent calcium phosphate stone disease, as well as growth retardation and rickets in children, or short stature and osteomalacia in adults. Renal dysfunction in renal tubular acidosis is not always confined to acid excretion and can be part of a more generalised renal tubule defect, as in the renal Fanconi syndrome. Isolated renal tubular acidosis is more usually acquired, due to drugs, autoimmune disease, post-obstructive uropathy or any cause of medullary nephrocalcinosis. Less commonly, it is inherited and may be associated with deafness, osteopetrosis or ocular abnormalities. The clinical classification of renal tubular acidosis has been correlated with our current physiological model of how the nephron excretes acid, and this has facilitated genetic studies that have identified mutations in several genes encoding acid and base ion transporters. In vitro functional studies of these mutant proteins in cell expression systems have helped to elucidate the molecular mechanisms underlying renal tubular acidosis, which ultimately may lead to new therapeutic options in what is still treatment only by giving an oral alkali. © 2005 Elsevier Ltd. All rights reserved
Localization of diuretic effects along the loop of Henle: an in vivo microperfusion study in rats
No full textIn order to clarify the effects on sodium reabsorption in the loop of Henle of methazolamide (a carbonic anhydrase inhibitor), chlorothiazide and the loop diuretics frusemide and bumetanide. superficial loops were perfused in vivo in anaesthetized rats and the individual diuretics were included in the perfusate. Differentiation between effects in the pars recta and in the thick ascending limb of Henle (TALH) was achieved by comparing responses to the diuretics when using a standard perfusate, designed to mimic native late proximal tubular fluid, and a low-sodium perfusate, designed to block net sodium reabsorption in the pars recta. With the standard perfusate, methazolamide caused decreases in sodium reabsorption (J(Na)) and water reabsorption (J(V)); with the low-sodium perfusate, a modest effect on J(Na) persisted, suggesting that carbonic anhydrase inhibition reduces sodium reabsorption in both the pars recta and the TALH. The effects of chlorothiazide were very similar to those of methazolamide with both the standard and low-sodium perfusates, suggesting that chlorothiazide also inhibits sodium reabsorption in the pars recta and TALH, perhaps through inhibition of carbonic anhydrase. With the standard perfusate, both frusemide and bumetanide produced the expected large decreases in J(Na), but J(V) was also lowered. With the low-sodium perfusate, the inhibitory effects of the loop diuretics, particularly those of frusemide, were substantially reduced, while net potassium secretion was found. These observations indicate that a significant component of the effect of frusemide (and possibly of bumetanide) on overall sodium reabsorption is located in the pars recta, and that loop diuretics induce potassium secretion in the TALH
Uric acid and the kidney: Urate transport, stone disease and progressive renal failure
No full textIn this brief review and update, we try to cover recent developments in our understanding of uric acid transport by the kidney, the contribution of uric acid to renal stone disease, its potential role in progressive renal failure and, most recently, the novel and as yet unexplained link between the urinary glycoprotein Tamm-Horsfall protein (uromodulin) and hyperuricaemia and two inherited forms of renal disease with chronic renal failure. © 2005 Bentham Science Publishers Ltd
Iothalamate measured by capillary electrophoresis is a suitable alternative to radiolabeled inulin in renal micropuncture
No full textIothalamate measured by capillary electrophoresis is a suitable alternative to radiolabeled inulin in renal micropuncture.BackgroundInulin remains the gold standard for measurements of fluid reabsorption (Jv) and single nephron glomerular filtration rate (SNGFR) in micropuncture experiments. However, the method used to measure cold inulin in nanoliter samples is time-consuming, while the use of radiolabeled inulin is disadvantaged by possible radioactive contamination, disposal of radioactive material and cost of the isotope. It has been reported that non-radiolabeled iothalamate may be a suitable alternative for estimation of whole kidney GFR. The present study tested whether iothalamate can be used to measure Jv in microperfusion and free-flow micropuncture experiments.MethodsSuperficial loops of Henle (LOH) were perfused from late proximal to early distal tubules with an end-like proximal solution. In the first set of experiments, the perfusate contained both iothalamate (1.9 mmol/L) and 3H-methoxy-inulin (50 μCi · mL-1). To test if iothalamate was able to detect changes in Jv, two additional sets of experiments were performed: (1) mannitol (61 mmol/L) was added to the perfusate to partially replace NaCl, a condition known inhibit Jv; (2) LOH of remnant kidneys were perfused, which in previous experiments we showed to have a higher Jv. Lastly, free-flow micropuncture experiments were performed by infusing iothalamate IV at 18.3 mg · h-1. Iothalamate analysis in nanoliter samples of renal tubular fluid obtained in vivo was performed by capillary electrophoresis (CE).ResultsIn the first set of experiments, liquid scintillation counting of 3H-methoxy-inulin versus iothalamate analysis with CE resulted in almost identical calculated perfusion rates (20.4 ± 0.6 vs. 20.6 ± 0.7 nL · min-1, N = 20) and tubular fluid/perfusate ratios (TF/P; 1.35 ± 0.04 vs. 1.36 ± 0.04) and thus also Jv (5.17 ± 0.50 vs. 5.38 ± 0.59 nL · min-1). In the mannitol experiments, iothalamate measurements showed that the addition of mannitol significantly reduced Jv from 4.98 ± 0.40 (N = 19) to 0.72 ± 0.58 nL · min-1 (N = 33; P < 0.0001). Iothalamate determinations by CE were able to detect a significant increase in Jv in LOH of remnant rats perfused at 40 nL · min-1[from to 8.40 ± 0.73 (N = 20) in sham-operated to 17.8 ± 2.9 nL · min-1 (N = 6) in remnant animals; P < 0.0001]. In free flow micropuncture experiments the ratio of tubular fluid to plasma iothalamate (TF/P) along the proximal tubule was 1.62 ± 0.10 (N = 15).ConclusionsThese data demonstrate that iothalamate can replace inulin to measure Jv in microperfusion and free-flow micropuncture experiments. Since iothalamate analysis by CE technique is a fast, easy and highly reproducible technique, it may become the gold standard method for the detection of fluid reabsorption in microperfused nephron segments
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