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Abstract
The kidney is one of the target organs that may show health disorders as a result of obesity. Obesity-related glomerulopathy (ORG) is a kidney disease category based on a biopsy diagnosis that may occur secondary to obesity. Detailed clinicopathologic observations of ORG have provided significant knowledge regarding obesity-associated renal complications. Glomerulomegaly with focal segmental glomerulosclerosis of perihilar locations is a typical renal histopathologic finding in ORG, which has long been considered to represent a state of single-nephron glomerular hyperfiltration. This hypothesis was recently confirmed in ORG patients by estimating single-nephron glomerular filtration rate using a combined image analysis and biopsy-based stereology. Overshooting in glomerulotubular and tubuloglomerular interactions may lead to glomerular hyperfiltration/hypertension, podocyte failure, tubular protein-traffic overload, and tubulointerstitial scarring, constituting a vicious cycle of a common pathway to the further loss of functioning nephrons and the progression of kidney functional impairment.
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Affiliation(s)
- Nobuo Tsuboi
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan.
| | - Yusuke Okabayashi
- Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
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Assessment of nephron number and single-nephron glomerular filtration rate in a clinical setting. Hypertens Res 2021; 44:605-617. [PMID: 33526913 DOI: 10.1038/s41440-020-00612-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 12/02/2020] [Accepted: 12/08/2020] [Indexed: 01/31/2023]
Abstract
Total nephron counts vary widely between individuals and may affect susceptibility to certain diseases, including hypertension and chronic kidney disease. Detailed analyses of whole kidneys collected from autopsy patients remain the only method for accurately counting nephrons in humans, with no equivalent option in living subjects. Current technological advances have enabled estimations of nephron numbers in vivo, particularly the use of total nephron number and whole-kidney glomerular filtration rate to estimate the mean single-nephron glomerular filtration rate. The use of this method would allow physicians to detect dynamic changes in filtration function at the single-nephron level rather than to simply count the number of nephrons that appear to be functioning. Currently available methods for estimating total nephron number in clinical practice have the potential to overcome limitations associated with autopsy analyses and may therefore pave the way for new therapeutic interventions and improved clinical outcomes.
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Denic A, Mathew J, Lerman LO, Lieske JC, Larson JJ, Alexander MP, Poggio E, Glassock RJ, Rule AD. Single-Nephron Glomerular Filtration Rate in Healthy Adults. N Engl J Med 2017; 376:2349-2357. [PMID: 28614683 PMCID: PMC5664219 DOI: 10.1056/nejmoa1614329] [Citation(s) in RCA: 212] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND The glomerular filtration rate (GFR) assesses the function of all nephrons, and the single-nephron GFR assesses the function of individual nephrons. How the single-nephron GFR relates to demographic and clinical characteristics and kidney-biopsy findings in humans is unknown. METHODS We identified 1388 living kidney donors at the Mayo Clinic and the Cleveland Clinic who underwent a computed tomographic (CT) scan of the kidney with the use of contrast material and an iothalamate-based measurement of the GFR during donor evaluation and who underwent a kidney biopsy at donation. The mean single-nephron GFR was calculated as the GFR divided by the number of nephrons (calculated as the cortical volume of both kidneys as assessed on CT times the biopsy-determined glomerular density). Demographic and clinical characteristics and biopsy findings were correlated with the single-nephron GFR. RESULTS A total of 58% of the donors were women, and the mean (±SD) age of the donors was 44±12 years. The mean GFR was 115±24 ml per minute, the mean number of nephrons was 860,000±370,000 per kidney, and the mean single-nephron GFR was 80±40 nl per minute. The single-nephron GFR did not vary significantly according to age (among donors <70 years of age), sex, or height (among donors ≤190 cm tall). A higher single-nephron GFR was independently associated with larger nephrons on biopsy and more glomerulosclerosis and arteriosclerosis than would be expected for age. A higher single-nephron GFR was associated with a height of more than 190 cm, obesity, and a family history of end-stage renal disease. CONCLUSIONS Among healthy adult kidney donors, the single-nephron GFR was fairly constant with regard to age, sex, and height (if ≤190 cm). A higher single-nephron GFR was associated with certain risk factors for chronic kidney disease and certain kidney-biopsy findings. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.).
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Affiliation(s)
- Aleksandar Denic
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - Jerry Mathew
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - Lilach O Lerman
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - John C Lieske
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - Joseph J Larson
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - Mariam P Alexander
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - Emilio Poggio
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - Richard J Glassock
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
| | - Andrew D Rule
- From the Divisions of Nephrology and Hypertension (A.D., J.M., L.O.L., J.C.L., A.D.R.), Biomedical Statistics and Informatics (J.J.L.), and Epidemiology (A.D.R.) and the Department of Laboratory Medicine and Pathology (J.C.L., M.P.A.), Mayo Clinic, Rochester, MN; the Department of Nephrology, Cleveland Clinic, Cleveland (E.P.); and the Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles (R.J.G.)
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Qian C, Yu X, Pothayee N, Dodd S, Bouraoud N, Star R, Bennett K, Koretsky A. Live nephron imaging by MRI. Am J Physiol Renal Physiol 2014; 307:F1162-8. [PMID: 25186296 DOI: 10.1152/ajprenal.00326.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The local sensitivity of MRI can be improved with small MR detectors placed close to regions of interest. However, to maintain such sensitivity advantage, local detectors normally need to communicate with the external amplifier through cable connections, which prevent the use of local detectors as implantable devices. Recently, an integrated wireless amplifier was developed that can efficiently amplify and broadcast locally detected signals, so that the local sensitivity was enhanced without the need for cable connections. This integrated detector enabled the live imaging of individual glomeruli using negative contrast introduced by cationized ferritin, and the live imaging of renal tubules using positive contrast introduced by gadopentetate dimeglumine. Here, we utilized the high blood flow to image individual glomeruli as hyperintense regions without any contrast agent. These hyperintense regions were identified for pixels with signal intensities higher than the local average. Addition of Mn(2+) allowed the simultaneous detection of both glomeruli and renal tubules: Mn(2+) was primarily reabsorbed by renal tubules, which would be distinguished from glomeruli due to higher enhancement in T1-weighted MRI. Dynamic studies of Mn(2+) absorption confirmed the differential absorption affinity of glomeruli and renal tubules, potentially enabling the in vivo observation of nephron function.
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Affiliation(s)
- Chunqi Qian
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland;
| | - Xin Yu
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland; High-Field Magnetic Resonance Department, Max Planck Institute for Biological Cybernetics, Tubingen, Germany
| | - Nikorn Pothayee
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Stephen Dodd
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Nadia Bouraoud
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Robert Star
- Division of Kidney Urologic and Hematologic Diseases, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Kevin Bennett
- Department of Biology, University of Hawaii, Honolulu, Hawaii; and
| | - Alan Koretsky
- Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland
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5
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Abstract
The kidney plays a fundamental role in maintaining body salt and fluid balance and blood pressure homeostasis through the actions of its proximal and distal tubular segments of nephrons. However, proximal tubules are well recognized to exert a more prominent role than distal counterparts. Proximal tubules are responsible for reabsorbing approximately 65% of filtered load and most, if not all, of filtered amino acids, glucose, solutes, and low molecular weight proteins. Proximal tubules also play a key role in regulating acid-base balance by reabsorbing approximately 80% of filtered bicarbonate. The purpose of this review article is to provide a comprehensive overview of new insights and perspectives into current understanding of proximal tubules of nephrons, with an emphasis on the ultrastructure, molecular biology, cellular and integrative physiology, and the underlying signaling transduction mechanisms. The review is divided into three closely related sections. The first section focuses on the classification of nephrons and recent perspectives on the potential role of nephron numbers in human health and diseases. The second section reviews recent research on the structural and biochemical basis of proximal tubular function. The final section provides a comprehensive overview of new insights and perspectives in the physiological regulation of proximal tubular transport by vasoactive hormones. In the latter section, attention is particularly paid to new insights and perspectives learnt from recent cloning of transporters, development of transgenic animals with knockout or knockin of a particular gene of interest, and mapping of signaling pathways using microarrays and/or physiological proteomic approaches.
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Affiliation(s)
- Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
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Leong PKK, Yang LE, Lin HW, Holstein-Rathlou NH, McDonough AA. Acute hypotension induced by aortic clamp vs. PTH provokes distinct proximal tubule Na+ transporter redistribution patterns. Am J Physiol Regul Integr Comp Physiol 2004; 287:R878-85. [PMID: 15205183 DOI: 10.1152/ajpregu.00180.2004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Renal parathyroid hormone (PTH) action is often studied at high doses (100 microg PTH/kg) that lower mean arterial pressure significantly, albeit transiently, complicating interpretation of studies. Little is known about the effect of acute hypotension on proximal tubule Na(+) transporters. This study aimed to determine the effects of acute hypotension, induced by aortic clamp or by high-dose PTH (100 microg PTH/kg), on renal hemodynamics and proximal tubule Na/H exchanger isoform 3 (NHE3) and type IIa Na-P(i) cotransporter protein (NaPi2) distribution. Subcellular distribution was analyzed in renal cortical membranes fractionated on sorbitol density gradients. Aortic clamp-induced acute hypotension (from 100 +/- 3 to 78 +/- 2 mmHg) provoked a 62% decrease in urine output and a significant decrease in volume flow from the proximal tubule detected as a 66% decrease in endogenous lithium clearance. There was, however, no significant change in glomerular filtration rate (GFR) or subcellular distribution of NHE3 and NaPi2. In contrast, high-dose PTH rapidly (<2 min) decreased arterial blood pressure to 51 +/- 3 mmHg, decreased urine output, and shifted NHE3 and NaPi2 out of the low-density membranes enriched in apical markers. PTH at much lower doses (<1.4 microg.kg(-1).h(-1)) did not change blood pressure and was diuretic. In conclusion, acute hypotension per se increases proximal tubule Na(+) reabsorption without changing NHE3 or NaPi2 subcellular distribution, indicating that trafficking of transporters to the surface is not the likely mechanism; in comparison, hypotension secondary to high-dose PTH blocks the primary diuretic effect of PTH but does not inhibit the PTH-stimulated redistribution of NHE3 and NaPi2 to the base of the microvilli.
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Affiliation(s)
- Patrick K K Leong
- Dept. of Physiology and Biophysics, Univ. of Southern California Keck School of Medicine, 1333 San Pablo St., Los Angeles, CA 90089-9142, USA
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8
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Nagashima K, Wu J, Kavouras SA, Mack GW. Increased renal tubular sodium reabsorption during exercise-induced hypervolemia in humans. J Appl Physiol (1985) 2001; 91:1229-36. [PMID: 11509520 DOI: 10.1152/jappl.2001.91.3.1229] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that renal tubular Na(+) reabsorption increased during the first 24 h of exercise-induced plasma volume expansion. Renal function was assessed 1 day after no-exercise control (C) or intermittent cycle ergometer exercise (Ex, 85% of peak O(2) uptake) for 2 h before and 3 h after saline loading (12.5 ml/kg over 30 min) in seven subjects. Ex reduced renal blood flow (p-aminohippurate clearance) compared with C (0.83 +/- 0.12 vs. 1.49 +/- 0.24 l/min, P < 0.05) but did not influence glomerular filtration rates (97 +/- 10 ml/min, inulin clearance). Fractional tubular reabsorption of Na(+) in the proximal tubules was higher in Ex than in C (P < 0.05). Saline loading decreased fractional tubular reabsorption of Na(+) from 99.1 +/- 0.1 to 98.7 +/- 0.1% (P < 0.05) in C but not in Ex (99.3 +/- 0.1 to 99.4 +/- 0.1%). Saline loading reduced plasma renin activity and plasma arginine vasopressin levels in C and Ex, although the magnitude of decrease was greater in C (P < 0.05). These results indicate that, during the acute phase of exercise-induced plasma volume expansion, increased tubular Na(+) reabsorption is directed primarily to the proximal tubules and is associated with a decrease in renal blood flow. In addition, saline infusion caused a smaller reduction in fluid-regulating hormones in Ex. The attenuated volume-regulatory response acts to preserve distal tubular Na(+) reabsorption during saline infusion 24 h after exercise.
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Affiliation(s)
- K Nagashima
- The John B. Pierce Laboratory, New Haven, Connecticut 06519, USA
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9
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Thomas SR, Dagher G. A kinetic model of rat proximal tubule transport--load-dependent bicarbonate reabsorption along the tubule. Bull Math Biol 1994; 56:431-58. [PMID: 7522077 DOI: 10.1007/bf02460466] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A model is presented of solute and water reabsorption along the proximal tubule of the rat kidney based on kinetic descriptions of the main membrane transport systems, in order to assess the extent to which these kinetics suffice to explain certain aspects of the global transport behaviour in this segment, especially with respect to bicarbonate reabsorption. The model includes in the apical membrane, an active proton pump, Na+/H+ antiport, Na-coupled transport of organic solutes, Cl-/formate exchange with formic acid recycling, and membrane conductances to protons and K+. In the baso-lateral membrane, besides the Na+/K+ pump, the model includes Na(+)-3HCO3- and electroneutral K(+)-Cl- cotransporters, and membrane conductances for K+, H+, and, optionally, for Cl-. Appropriate passive diffusional pathways were included in both cell membranes and in the paracellular pathway. Using mass balance and electroneutrality constraints, these transport systems were built into an epithelial model which was then integrated (by finite difference approximation) into a model of a longitudinal tubule. Simulated cellular solute concentrations and luminal concentration profiles were in good agreement with reported experimental observations. We show that, given the reported transport kinetics for the Na+/H+ antiporter, a hitherto unexplained observation concerning load-dependent bicarbonate reabsorption can be shown mainly to result from the nonlinear longitudinal concentration profile for bicarbonate and pH. We also discuss problems of transcellular Cl- transport in the light of recent reports of basolateral Cl- conductance and observations relevant to apical Cl-/formate (or other base) exchange.
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Affiliation(s)
- S R Thomas
- INSERM U.323, Faculté de Médecine Necker, Paris, France
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Ahlgren G, Månsson W, White T. Renal parenchymal function evaluated by scintillation camera renography before and after pyeloplasty for hydronephrosis. SCANDINAVIAN JOURNAL OF UROLOGY AND NEPHROLOGY 1992; 26:161-8. [PMID: 1626206 DOI: 10.1080/00365599.1992.11690448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Scintillation camera renography with Tc-DTPA was performed before and after pyeloplasty on 16 kidneys with urographic signs of pelviureteric obstruction causing hydronephrosis. Regional parenchymal renograms were generated, and the passage of Tc-DTPA through the parenchyma was measured and correlated to the change in separate glomerular filtration rate. Preoperative parenchymal passage of DTPA was significantly slower (p = 0.02) in kidneys with improved glomerular filtration rate after pyeloplasty than in those without such improvement. Postoperative passage of DTPA in parenchyma was almost identical with that in a reference series. This method seems to be clinically useful for evaluating cases of hydronephrosis and for predicting the outcome of pyeloplasty.
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Affiliation(s)
- G Ahlgren
- Department of Urology, University of Lund, Sweden
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11
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Ichikawi I, Harris RC. Angiotensin actions in the kidney: renewed insight into the old hormone. Kidney Int 1991; 40:583-96. [PMID: 1745006 DOI: 10.1038/ki.1991.249] [Citation(s) in RCA: 204] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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12
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Britton KE, Nawaz MK, Whitfield HN, Nimmon CC, Carroll MJ, Granowska M, Mlodkowska E. Obstructive nephropathy: comparison between parenchymal transit time index and frusemide diuresis. BRITISH JOURNAL OF UROLOGY 1987; 59:127-32. [PMID: 3548874 DOI: 10.1111/j.1464-410x.1987.tb04802.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Sixty-three patients presenting with the clinical problem of renal outflow disorder were studied using 99mTc DTPA. The techniques of frusemide diuresis and parenchymal transit time index analysis were compared and both shown to be successful in aiding the decision as to the presence or absence of significant outflow obstruction.
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Roos JC, Kirchner KA, Abernethy JD, Langford HG. Differential effect of salt loading on sodium and lithium excretion in Dahl salt-resistant and -sensitive rats. Hypertension 1984; 6:420-4. [PMID: 6735461 DOI: 10.1161/01.hyp.6.3.420] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Fractional excretion of lithium, as a marker for proximal sodium reabsorption, was determined in normotensive Dahl S rats (susceptible to NaCl hypertension) and Dahl R rats (resistant to NaCl hypertension) before and following an acute sodium load. Baseline mean arterial pressures, inulin clearances, sodium excretion rates, and fractional lithium clearances were not different between the R and S rats. Following the salt loading and despite similar mean arterial pressures and degree of volume expansion, the glomerular filtration rate, urinary flow rates, and absolute sodium excretion rates were greater in R than S rats. The fractional excretion of lithium was also greater in R than S rats. These data demonstrate that, at equal mean arterial pressures, Dahl S rats have a reduced capacity for sodium excretion, and that this defect is present prior to the development of hypertension. Furthermore, the observation that these animals also have a lower fractional lithium excretion during volume expansion suggests that salt loading reduces proximal tubule reabsorption to a lesser extent in Dahl S than R rats. These data suggest that the subnormal sodium and water excretion observed after sodium loading in S rats may be partially due to an abnormality in proximal tubule sodium handling.
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14
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Häberle DA, Shiigai TT, Maier G, Schiffl H, Davis JM. Dependency of proximal tubular fluid transport on the load of glomerular filtrate. Kidney Int 1981; 20:18-28. [PMID: 7300109 DOI: 10.1038/ki.1981.99] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In hydropenic rats, the reabsorption of glomerular filtrate by the proximal convoluted tubules was measured before and after reduction of its intratubular flow rate. Three different protocols were used. (1) In 26 tubules (14 rats), nephron glomerular filtration rate (SNGFR) was varied from 37.2 +/- 7.3 to 20.4 +/- 7.1 nl/min by microperfusing their loops of Henle at 0 to 5 nl/min and 40 nl/min, respectively. This 43% reduction of SNGFR was followed by a 36.0 +/- 23.3% reduction of volume reabsorption rate (P less than 0.001). Between both parameters a linear regression line can be calculated, which is given by y = 0.92 chi + 0.0017. (2) In 17 tubules (14 rats), SNGFR was altered again by feedback from 46.0 +/- 9.7 to 28.8 +/- 9.3 nl/min. The volume resorption from the first half of the proximal convoluted tubule was compared with the reabsorption in its late proximal segments, which were microperfused with proximal tubular fluid at a rate of 20 nl/min. The 36.8% reduction of SNGFR was followed by only a 28.2% reduction of volume reabsorption rate in the first half of the tubule. In the microperfused segments, however, reabsorption remained unaltered. (3) In 29 tubules (21 rats), at the midpoint of proximal convolutions, some of the tubule fluid was removed by a suction pump, and volume reabsorption rate in the late segments was compared with that in the early parts of this tubule, when SNGFR remained stable. The reduction of intratubular flow from 27.7 +/- 8.5 to 14.7 +/- 5.8 nl/min, which is 53% of control, were followed by a reduction of volume reabsorption rate in the late segment to 60.6% control. Between both parameters a regression line was calculated, which is given by y = 0.76 chi +/- 0.01. We conclude that the rate of volume reabsorption by the proximal tubule depends on its intratubular load of glomerular filtrate and, further, that this dependency accounts predominantly for the maintenance of glomerular tubular balance under conditions of hydropenia.
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Britton KE, Nimmon C, Whitfield HN. The dilated upper urinary tract. BRITISH MEDICAL JOURNAL 1979; 2:49. [PMID: 466268 PMCID: PMC1595771 DOI: 10.1136/bmj.2.6181.49-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Abstract
A mathematical model of the nephron was developed by writing a set of material balance equations for the flow of urea, salt and water along the foregoing study and are taken here as a basis, in particular the model configuration of the collecting duct system. The stimulation of the model equatentration profiles which at the ends of the several tubular sections were consistent with the values observed in experimental investigations.e medullary interstitial solute concentration profiles are taken to increase linearly in outer and inner zone. The several transeptithelial fluxes are driven by diffusion, osmosis, solvent drag and active transport. The development of osmotic gradient in the inner medulla is taken here to be caused by active secretion of salt into the descending LImb of Henle's loop. The parameters in the flux equations for all parts of the nephron and the concentration values at the end of each tubular section are determined by collecting and averaging the values given in literature and by extrapolating the measurement data. The simulation of the model equations with these averaged parameters resulted in concentration profiles which at the ends of the several tubular sections were consistent with the values observed in experimental investigations.
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Oatley K. Control of water-excretion by antidiuretic hormone: some aspects of modelling the system. Med Biol Eng Comput 1977; 15:579-88. [PMID: 203778 DOI: 10.1007/bf02457914] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Cohen JJ, Little JR. Lactate metabolism in the isolated perfused rat kidney: relations to renal function and gluconeogenesis. J Physiol 1976; 255:399-414. [PMID: 1255526 PMCID: PMC1309254 DOI: 10.1113/jphysiol.1976.sp011286] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In the intact dog, decreases in both glomerular filtration rate and net renal Na+ reabsorption due to raised ureteral pressure were not associated with a decrease in renal lactate oxidation rate, although total renal CO2 production decreased in proportion to the changes in net renal reabsorption of Na+ and glomerular filtration rate. 2. In order to determine whether, in the absence of other added substrates, the metabolism of lactate supports only the 'basal' renal metabolism or can enhance renal function as well, the rate of lactate utilization and decarboxylation by the isolated perfused rat kidney have been quantified in relation to renal function and one measure of renal basal metabolism, glucose production. 3. The perfusate was Krebs-Ringer bicarbonate (pH 7-35-7-48) with Fraction V bovine serum albumin, 6g/100 ml. L-(+)-lactate was added to raise the lactate concentration from endogenous levels to 2-5, 5-0 or 10 mM. 4. We determined: net lactate utilization rate, lactate decarboxylation rate (14CO2 produced from L-(+)-[U-14C]lactate), net glucose production rate, and net re-absorptive rate of Na+. 5. The apparent Km and Vmax for lactate oxidation were 2-1 mM and 1-29 mumole.g-1.min-1 respectively. There was no apparent maximum for total lactate utilization rate due to continuing increases in glucose production rate as lactate concentration was raised. At ca. 10 mM lactate, glucose production accounted for about half of the total lactate utilized. Therefore the basal energy requirements of the kidney need not be constant since glucose production increases as lactate concentration is raised. 6. Both lactate oxidation rate and lactate utilization rate were significantly correlated with the net reabsorption of Na+ by the renal tubules, with the percentage of filtered Na+ reabsorbed and with the glomerular filtration rate. The major fraction of the net renal reabsorption of Na+ was probably supported by the metabolism of substrates either bound to albumin or derived from renal tissue since the percentage of filtered Na+ reabsorbed increased from ca. 78%, when no lactate was added, to 97% when initial lactate concentration was 10 mM. Therefore, addition of lactate increased both the basal mebabolism and tubular function. However, these observations do not permit us to conclude whether it was the presence of lactate, or its utilization by oxidative or by other pathways which enhanced net renal reabsorption of Na+ and the glomerular filtration rate.
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Maddox DA, Bennett CM, Deen WM, Glassock RJ, Knutson D, Brenner BM. Control of proximal tubule fluid reabsorption in experimental glomerulonephritis. J Clin Invest 1975; 55:1315-25. [PMID: 1133177 PMCID: PMC301887 DOI: 10.1172/jci108051] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
We have recently shown that in the early autologous phase of nephrotoxic serum nephritis (NSN) single nephron glomerular filtration rate is unchanged from values in normal hydropenic control rats, but that single nephron filtration fraction and efferent arteriolar oncotic pressure (piE) are reduced because of a marked reduction in the glomerular capillary ultrafiltration coefficient. The present study was undertaken to examine the influence of this decline in piE as well as the other known determinants of peritubular capillary fluid exchange on absolute proximal fluid reabsorption (APR) in NSN. The findings indicate that APR and proximal fractional reabsorption are reduced significantly in NSN, relative to values in a separate group of age and weight-matched normal hydropenic control rats studied concurrently. In addition to the measured decline in piE, efferent arteriolar plasma flow (Qe) and peritubular capillary hydraulic pressure (Pc) were found to increase significantly, while interstitial oncotic pressure, estimated from hilar lymph, was not significantly different from values in control rats. Using a mathematical model of peritubular capillary fluid uptake we found that, assuming that the capillary permeability-surface area product and interstitial hydraulic pressure are unchanged in NSN, the observed changes in piE and Pc are sufficient to offset the effect of the increase in QE, yielding a calculated reduction in APR of approximately 4 nl/min, in excellent agreement with the observed mean decline of 4.1 nl/min. These findings suggest that control of APR in NSN is mediated by the same factors that regulate APR under normal physiological conditions, namely, the imbalance of forces governing peritubular capillary uptake of isotonic reabsorbate.
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21
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Clausen G, Tyssebotn I. Single-nephron filtration during hemorrhagic hypotension in the conscious rat. ACTA PHYSIOLOGICA SCANDINAVICA 1974; 92:364-73. [PMID: 4454994 DOI: 10.1111/j.1748-1716.1974.tb05754.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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22
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Purkerson ML, Rolf DB, Chase LR, Slatopolsky E, Klahr S. Tubular reabsorption of phosphate after release of complete ureteral obstruction in the rat. Kidney Int 1974; 5:326-36. [PMID: 4372448 DOI: 10.1038/ki.1974.48] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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23
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Dev B, Drescher C, Schnermann J. Resetting of tubulo-glomerular feedback sensitivity by dietary salt intake. Pflugers Arch 1974; 346:263-77. [PMID: 4856389 DOI: 10.1007/bf00596182] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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24
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Anagnostopoulos T, Velu E. Electrical resistance of cell membranes in Necturus kidney. Pflugers Arch 1974; 346:327-39. [PMID: 4856393 DOI: 10.1007/bf00596188] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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25
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26
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Deen WM, Troy JL, Robertson CR, Brenner BM. Dynamics of glomerular ultrafiltration in the rat. IV. Determination of the ultrafiltration coefficient. J Clin Invest 1973; 52:1500-8. [PMID: 4703234 PMCID: PMC302415 DOI: 10.1172/jci107324] [Citation(s) in RCA: 175] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Pressures and flow rates were measured in accessible surface glomeruli of mutant Wistar rats under conditions deliberately designed to prevent achievement of filtration pressure equilibrium, that is, the equalization of transcapillary hydrostatic and oncotic pressures by the efferent end of the glomerulus as typically observed in the normal hydropenic rat. Disequilibrium was obtained at elevated levels of glomerular plasma flow (GPF) brought about by acute expansion of plasma volume with a volume of rat plasma equal to 5% of body weight. Glomerular hydrostatic and oncotic pressures measured at high GPF were used to calculate the ultrafiltration coefficient, K(f), the product of effective hydraulic permeability and surface area. GPF was then either lowered (by aortic constriction) or raised (by carotid occlusion) in order to examine the dependence of K(f) on GPF. The value of K(f) per glomerulus, 0.08 nl/(s.mm Hg), was found not to vary over an approximately twofold range of GPF. This finding, taken together with data from previous studies from this laboratory, leads us to conclude that plasma-flow dependence of glomerular filtration rate (GFR) results primarily from flow-induced changes in mean ultrafiltration pressure, rather than large changes in K(f).
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27
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Bartoli E, Conger JD, Earley LE. Effect of intraluminal flow on proximal tubular reabsorption. J Clin Invest 1973; 52:843-9. [PMID: 4693649 PMCID: PMC302331 DOI: 10.1172/jci107248] [Citation(s) in RCA: 44] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Micropuncture techniques in the rat were used to reinvestigate the possibility that intraluminal flow rate per se may influence net volume reabsorption by the proximal tubule. An experimental design was devised which lowered intraluminal flow without affecting filtration rate of the nephron under study or without directly affecting other renal hemodynamics. In 11 rats flow of tubular fluid between early and late proximal tubular sites was reduced by partially collecting tubular fluid at the early puncture site. In 42 nephrons the rate of flow of tubular fluid was reduced an average of 45% without changing nephron filtration rate and there was an associated reduction in reabsorption between the two sites which averaged 29%. This indicated 63% balance between delivery of tubular fluid and the rate of reabsorption between two sites along proximal tubules. The results of these studies indicate that a reduction in delivery of normal filtrate along the proximal tubule is associated with a concordant reduction in the absolute rate of reabsorption. Since this relationship occurred in the absence of changes in renal hemodynamics or even a change in filtration rate of the nephron under study it is concluded that changes in intraluminal load per se play an important role in the phenomenon of glomerulotubular balance.
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Brenner BM, Troy JL, Daugharty TM, MacInnes RM. Quantitative importance of changes in postglomerular colloid osmotic pressure in mediating glomerulotubular balance in the rat. J Clin Invest 1973; 52:190-7. [PMID: 4682382 PMCID: PMC302242 DOI: 10.1172/jci107164] [Citation(s) in RCA: 44] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
In recent studies in this laboratory employing normal hydropenic rats we have demonstrated that the reduction in absolute proximal reabsorption that attends the experimental reduction of single nephron glomerular filtration rate (SNGFR) (glomerulotubular balance) is mediated, at least in part, by the accompanying decline in postglomerular vascular protein concentration, and therefore, postglomerular colloid osmotic pressure (piEA). The present study was undertaken to define the quantitative contribution of these changes in piEA to the changes in absolute proximal reabsorption measured under these conditions. A protocol was employed which enabled us to examine the effects on absolute proximal reabsorption of reductions in filtered load brought about under conditions in which piEA remained essentially unchanged. Thus, after partial aortic constriction in 16 plasma-loaded rats, near constancy of piEA was observed in 10 (a change in efferent arteriolar protein concentration of 0.4 g/100 ml or less) and in these, uniform reductions in SNGFR averaging 16.7 nl/min were attended by reductions in absolute proximal reabsorption averaging only 1.7 nl/min, or 7% of preconstriction values. These findings, taken together with previous observations from this laboratory, suggest that the proximal reabsorptive adjustment that characterizes glomerulotubular balance in the rat is markedly blunted when changes in piEA are prevented. In the remaining six rats, a mean reduction in filtered load comparable to that observed in the above group was attended by slightly to moderately greater reductions in efferent arteriolar protein concentration, thereby fulfilling less well the stated aim of this study. Nevertheless, in accord with the above conclusion, these relatively greater reductions in piEA were accompanied by correspondingly greater reductions in absolute proximal reabsorption.
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Lang F, Greger R, Deetjen P. Handling of uric acid by the rat kidney. 3. Microperfusion studies on steady state concentration of uric acid in the proximal tubule. Consideration of free flow conditions. Pflugers Arch 1973; 338:295-302. [PMID: 4734842 DOI: 10.1007/bf00586071] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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30
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Elmer M, Eskildsen PC, Kristensen LO, Leyssac PP. A comparison of renal function in rats anesthetized with inactin and sodium amytal. ACTA PHYSIOLOGICA SCANDINAVICA 1972; 86:41-58. [PMID: 4638319 DOI: 10.1111/j.1748-1716.1972.tb00224.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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31
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Wilson DR. Micropuncture study of chronic obstructive nephropathy before and after release of obstruction. Kidney Int 1972; 2:119-30. [PMID: 4669448 DOI: 10.1038/ki.1972.82] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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32
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Staum BB, Hamburger RJ, Goldberg M. Tracer microinjection study of renal tubular phosphate reabsorption in the rat. J Clin Invest 1972; 51:2271-6. [PMID: 4639013 PMCID: PMC292391 DOI: 10.1172/jci107036] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
To determine the sites of tubular phosphate reabsorption in the nephron, microinjection studies were undertaken, utilizing isotonic electrolyte solutions, containing either 1.4 or 8.0 mM phosphate and radioactive PO(4)-(33)P and inulin-(3)H, in rats made mildly diuretic by infusion of mannitol. The injected sites were localized by the technique of latex dissection. The relation between proximal tubular length and per cent (33)P recovery for injections of 1.4 mM phosphate (physiological amounts) suggest that relatively little reabsorption of phosphate occurs in the distal 30% of the proximal tubule compared with the proximal portion of the tubule. The corresponding recoveries for proximal tubular microinjections of 8.0 mM phosphate fall along a smooth curve tending to plateau with essentially complete (33)P recovery (> 95%) beyond 50% of the tubule. Absolute reabsorption of injected phosphate for both concentrations (i.e., absolute efflux per unit tubular length in the proximal tubule) was independent of phosphate delivery, since the relationship between reabsorption and site of injection was no different for the two concentrations. Distal convoluted tubular microinjections for both phosphate concentrations showed complete recovery of (33)P from all injection sites. THE DATA INDICATE THAT: (a) no phosphate reabsorption occurs in the distal convoluted tubule or in the collecting duct, (b) phosphate efflux per unit tubular length is greater in the first one-third of the proximal tubule than in the remaining two-thirds, and (c) in the last two-thirds of the proximal tubule, absolute phosphate reabsorption is relatively small and might be limited by factors other than the amount or concentration of injected phosphate.
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33
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Schultze RG, Weisser F, Bricker NS. The influence of uremia on fractional sodium reabsorption by the proximal tubule of rats. Kidney Int 1972; 2:59-65. [PMID: 4671529 DOI: 10.1038/ki.1972.72] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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34
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Adetuyibi A, Mills IH. Relation between urinary kallikrein and renal function, hypertension, and excretion of sodium and water in man. Lancet 1972; 2:203-7. [PMID: 4114209 DOI: 10.1016/s0140-6736(72)91636-4] [Citation(s) in RCA: 114] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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35
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Michael UF, Barenberg RL, Chavez R, Vaamonde CA, Papper S. Renal handling of sodium and water in the hypothyroid rat. Clearance and micropuncture studies. J Clin Invest 1972; 51:1405-12. [PMID: 5024038 PMCID: PMC292277 DOI: 10.1172/jci106936] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Hypothyroid rats were examined with conventional renal clearance and micropuncture techniques to elicit the mechanism and site within the nephron responsible for the increased salt and water excretion observed in these animals. When compared with age-matched control rats, a decrease in inulin clearance of 30% (P < 0.001) and in Hippuran clearance of 32% (P < 0.005) was observed in the hypothyroid rats. Absolute excretion of sodium and water was increased 3-fold (P < 0.02) and 2-fold (P < 0.025), respectively, while fractional excretion of sodium and water was increased 4.3-fold (P < 0.02) and 2.9-fold (P < 0.05), respectively, in the hypothyroid animals. Fractional proximal reabsorption of sodium as assessed from proximal tubular fluid to plasma ratios of inulin ([TF/P](IN)) was found to be decreased by 28% (P < 0.001) in the hypothyroid rats. Superficial single nephron filtration rate was reduced proportionately to the decrease in total filtration rate in the hypothyroid rats. These data indicate that the proximal tubule is one of the sites of diminished sodium and water reabsorption in the hypothyroid rat. The data also suggest that the observed decrease in glomerular filtration rate in the hypothyroid animals is not caused by a decrease in the number of functioning nephrons and that the observed increase in sodium and water excretion is not caused by a redistribution of filtrate from juxtamedullary to superficial nephrons. Although the exact mechanisms of the observed changes in proximal tubular function remain unknown, the data suggest that they are probably related to the lack of thyroid hormone. Whatever their mechanism, it appears that the enhanced sodium and water excretion observed in the hypothyroid animals must be determined by further reduction in tubular sodium reabsorption in the distal nephron.
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Asbury MJ, Gatenby PB, O'Sullivan S, Bourke E. Bumetanide: potent new "loop" diuretic. BRITISH MEDICAL JOURNAL 1972; 1:211-3. [PMID: 4550872 PMCID: PMC1789187 DOI: 10.1136/bmj.1.5794.211] [Citation(s) in RCA: 84] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Bumetanide, a pharmacologically new diuretic, was evaluated in 27 subjects. Its onset of action was within 30 minutes with a peak at 90 minutes and a total duration of action of about 270 minutes. In a controlled study in oedematous patients it was equipotent with frusemide at one-fortieth the molar dosage and did not differ from frusemide with regard to its pattern of electrolyte excretion. On continuous oral administration for eight days it produced effective diuresis with minimal alteration in biochemical and haematological status. The only adverse effect was gastric discomfort in one patient.
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39
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Baines AD. Effect of extracellular fluid volume expansion on maximum glucose reabsorption rate and glomerular tubular balance in single rat nephrons. J Clin Invest 1971; 50:2414-25. [PMID: 5096524 PMCID: PMC292184 DOI: 10.1172/jci106740] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Extracellular fluid volume expansion with isotonic saline (7.5% of body weight) decreased maximum glucose reabsorption rate by rat kidneys at plasma glucose concentrations greater than 30 mM. Glucose reabsorption rate was 30.2 +/-1.6 (SE) mumoles/min.g kidney in nonexpanded rats; it was 18.4 +/-1.5 mumoles/min.g in volume-expanded rats. Glucose reabsorption determined by micropuncture was 92% complete at the end of accessible superficial proximal convolutions. Volume expansion resulted in a slight but statistically insignificant reduction of maximal glucose reabsorption rate in superficial nephrons from 786 +/-35 mumumoles/min.g kidney in nonexpanded rats to 720 +/-30 mumumoles/min.g in volume-expanded rats. Superficial nephron filtration rate was increased by volume expansion from 28.8 +/-1.2 nl/min.g to 36.6 +/-1.5 nl/min.g kidney. In nonexpanded rats, the ratio of glucose reabsorption to glomerular filtration (tmg/sgfr) was similar in superficial and juxtamedullary nephrons. In volume-expanded rats superficial nephron tmg/sgfr was greater than juxtamedullary nephron tmg/sgfr. Juxtamedullary nephron function was measured by puncturing loops of Henle in the exposed papillae of small rats. Volume expansion increased sgfr without much effect on tmg in superficial nephrons while it decreased tmg without much effect on sgfr in deep nephrons. Physical changes produced by volume expansion seem to exert their greatest effect on proximal tubular function in the inner cortex. The increase in heterogeneity of glomerular-tubular balance could account for increased splay of glucose titration curves previously reported to accompany volume expansion.
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40
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Auld RB, Alexander EA, Levinsky NG. Proximal tubular function in dogs with thoracic caval constriction. J Clin Invest 1971; 50:2150-8. [PMID: 5116206 PMCID: PMC292149 DOI: 10.1172/jci106709] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The effect of saline infusion on proximal sodium reabsorption was compared in normal dogs and in dogs with acute or chronic partial thoracic vena cava obstruction. After acute vena cava obstruction, proximal fractional sodium reabsorption rose by 74%. During continued caval obstruction, saline loading strikingly reduced proximal reabsorption but sodium excretion remained minimal. In chronic caval dogs, saline loading reduced proximal fractional sodium reabsorption by 31% but sodium excretion in the micropunctured kidney was only 41 muEq/min. After saline infusion in normal dogs, proximal fractional sodium reabsorption fell 39% while unilateral sodium excretion rose to 584 muEq/min. Nephron filtration rate was also measured before and after saline loading in normal and chronic caval dogs in both repunctured and fresh tubules. There was a marked increase in nephron filtration rate in repunctured tubules and no change in freshly punctured tubules in both groups. The effect of saline loading on nephron filtration rate in normal and chronic caval dogs was similar, therefore, whether repunctured or fresh nephrons were considered.We conclude that saline infusion depresses proximal sodium reabsorption in acute and chronic TVC dogs. Since saline loading markedly increases distal delivery without a concomitant natriuresis, enhanced distal reabsorption must play a major role in the sodium retention exhibited by chronic caval dogs. Redistribution of filtrate does not appear to be a factor in this sodium retention.
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41
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Bartoli E, Earley LE. The relative contributions of reabsorptive rate and redistributed nephron filtration rate to changes in proximal tubular fractional reabsorption during acute saline infusion and aortic constriction in the rat. J Clin Invest 1971; 50:2191-203. [PMID: 5116209 PMCID: PMC292154 DOI: 10.1172/jci106714] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The absolute rate of reabsorption by superficial rat proximal tubules was measured by the in situ microperfusion technique under conditions of hydropenia, infusion of saline, and infusion of saline plus aortic constriction sufficient to decrease whole kidney filtration rate below hydropenic levels. Fractional reabsorption was measured in adjacent filtering nephrons by collecting and recollecting tubular fluid from late proximal convolutions during each experimental condition. During hydropenia, the absolute rate of proximal tubular reabsorption averaged 3.56 +/-0.60 nl/min per mm and late proximal tubular fractional reabsorption averaged 0.56 +/-0.10. From these two measurements and measurements of tubule length to the site of micropuncture, a value for filtration rate was calculated for filtering nephrons. During hydropenia this value averaged 32.9 +/-7.1 nl/min. Saline infusion increased sodium excretion to 5.5% of the filtered load as the absolute rate of proximal tubular reabsorption decreased 38% and fractional reabsorption decreased 45%. Calculated superficial nephron filtration rate increased 21% which on the average was identical with the simultaneously measured increase in whole kidney filtration rate. Similar results were obtained in a separate group of animals by the technique of total collection of late proximal tubular fluid. Aortic constriction during saline infusion decreased whole kidney and calculated nephron filtration rate to the same degree and to values lower than those during hydropenia. Fractional reabsorption increased but not to hydropenic values. The persistent natriuresis during aortic constriction was associated with a continued depression of the absolute rate of proximal tubular reabsorption which was sufficient to maintain an increased delivery of filtrate out of the proximal tubule despite the fall in nephron filtration rate. These results indicate that depressed fractional reabsorption in the proximal tubule during acute saline infusion is due predominantly to a decrease in absolute reabsorptive rate and to a lesser extent to an increase in superficial nephron filtration rate which is proportional to the increase in whole kidney filtration. Continued natriuresis when filtration rate is decreased during saline infusion can be accounted for entirely by the persistent large reduction in the absolute rate of proximal tubular reabsorption.
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42
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43
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Brenner BM, Troy JL, Daugharty TM. On the mechanism of inhibition in fluid reabsorption by the renal proximal tubule of the volume-expanded rat. J Clin Invest 1971; 50:1596-602. [PMID: 5125390 PMCID: PMC442058 DOI: 10.1172/jci106647] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We undertook to determine the extent to which the inhibition in absolute proximal fluid reabsorption in response to expansion of extracellular volume with noncolloid-containing solutions is the result of concomitant reductions in postglomerular (efferent arteriolar) protein concentration. Selective elevation of efferent arteriolar oncotic pressure in volume-expanded rats (Ringer's 10% body weight) to levels slightly in excess of normal by microperfusion with 9-10% albumin-Ringer's solution nearly completely reversed the inhibition in absolute and fractional reabsorption in adjacent proximal tubules. In contrast, during similar microperfusion with a 6-7% albumin solution, no increase in proximal reabsorption was measured. We interpret these findings to indicate that the bulk of the inhibition in absolute proximal reabsorption in response to volume expansion with colloid-free solutions is causally mediated by the accompanying parallel decline in postglomerular vascular protein concentration.
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44
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45
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Wedeen RP, Goldstein M, Levitt MF. Mechanisms of edema and the use of diuretics. Pediatr Clin North Am 1971; 18:561-76. [PMID: 4939564 DOI: 10.1016/s0031-3955(16)32566-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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46
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Mandin H, Israelit AH, Rector FC, Seldin DW. Effect of saline infusions on intrarenal distribution of glomerular filtrate and proximal reabsorption in the dog. J Clin Invest 1971; 50:514-22. [PMID: 5545118 PMCID: PMC291958 DOI: 10.1172/jci106520] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The effect of acute extracellular volume expansion with saline on the intrarenal distribution of glomerular filtrate, was studied in dogs utilizing micropuncture techniques in which samples were obtained by both recollection and from new tubules. Recollection was examined in seven dogs during continuous hydropenia and in five dogs during continuous saline diuresis. Recollection was associated with an increase in nephron flow rate of 8% during hydropenia and 27% during saline diuresis. In addition, during continuous saline diuresis, shortened transit times and lowered intratubular pressures were recorded in previously punctured tubules. Despite increased tubular flow, fractional reabsorption was unchanged. Nephron glomerular filtration rates (gfr) were measured during hydropenia and then after acute volume expansion in 10 dogs. In the repunctured tubules gfr rose 38% more than total glomerular filtration rate (GFR). In contrast, when new tubules were punctured during volume expansion, nephron gfr and total GFR changed proportionately. The disproportionate rise in nephron gfr after volume expansion noted with the recollection technique appears to be artifactual when contrasted to micropuncture of new tubules. With acute volume expansion, fractional reabsorption decreased 15% in recollected samples and 16% in newly sampled tubules. Increased nephron gfr cannot account for the fall in fractional reabsorption. It is concluded that in dogs, saline diuresis is not associated with redistribution of filtrate from deep to superficial nephrons, and that the fall in proximal fractional reabsorption is caused by diminished absolute reabsorption.
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47
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Brenner BM, Troy JL. Postglomerular vascular protein concentration: evidence for a causal role in governing fluid reabsorption and glomerulotublar balance by the renal proximal tubule. J Clin Invest 1971; 50:336-49. [PMID: 5540173 PMCID: PMC291930 DOI: 10.1172/jci106501] [Citation(s) in RCA: 136] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
We tested the relationship between postglomerular microvascular protein concentration and rates of sodium and water transfer by rat proximal tubules. Using recently described microperfusion techniques, efferent arterioles and branch peritubular capillaries of normal hydropenic rats were perfused with colloid-free Ringer's solution, and isoncotic (9.0-10.0 g/100 ml) and hyperoncotic (15 g/100 ml) albumin-Ringer's solutions. Reabsorption in adjacent proximal tubules was studied using free-flow techniques, with initial collections obtained during normal blood perfusion, recollections during experimental microperfusion, and in some tubules, repeat recollections after microperfusion and spontaneous resumption of blood perfusion. Colloid-free perfusion resulted in a uniform inhibition of proximal reabsorption (absolute and fractional). Despite identical techniques, substitution of isoncotic and hyperoncotic perfusates resulted, on average, in unchanged and increased rates of reabsorption, respectively. These findings of direct linear changes in reabsorption in response to changes in postglomerular protein concentrations usually occurred in the absence of significant changes in filtered load, and were nearly always found to be reversible within minutes of cessation of experimental perfusion. Given this evidence of a causal relationship between postglomerular oncotic pressure and proximal reabsorption, we undertook to determine whether this relationship is responsible for the parallel adjustments in proximal reabsorption that follow changes in GFR (glomerulotubular balance). Using a separate group of hydropenic rats, proximal reabsorption was studied, initially during partial aortic constriction (during which renal perfusion pressure, single nephron GFR, absolute proximal reabsorption, and calculated filtration fraction all were reduced below levels prior to constriction), and again while adjacent efferent arteriolar and peritubular capillary protein concentrations, but not GFR, were restored to normal (preconstriction) levels by microperfusion with 9-10 g/100 ml albumin-Ringer's solution. During this dissociation of GFR and postglomerular protein concentration, absolute and fractional proximal reabsorption nearly always increased in parallel with the changes in the latter, thereby demonstrating that glomerulotubular balance is mediated, at least in part, by changes in postglomerular oncotic pressure brought about by changes in filtration fraction.
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Morgan T. Factors controlling sodium transport in the proximal tubule and their relevance to clinical medicine. Med J Aust 1971; 1:118-21. [PMID: 5541594 DOI: 10.5694/j.1326-5377.1971.tb87470.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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49
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Schnermann J, Davis JM, Wunderlich P, Levine DZ, Horster M. Technical problems in the micropuncture determination of nephron filtration rate and their functional implications. Pflugers Arch 1971; 329:307-20. [PMID: 5167465 DOI: 10.1007/bf00588002] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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50
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Radtke HW, Rumrich G, Klöss S, Ullrich KJ. Influence of luminal diameter and flow velocity on the isotonic fluid absorption and 36Cl permeability of the proximal convolution of the rat kidney. Pflugers Arch 1971; 324:288-96. [PMID: 5103162 DOI: 10.1007/bf00592457] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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