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Motta SE, Imenez Silva PH, Daryadel A, Haykir B, Pastor-Arroyo EM, Bettoni C, Hernando N, Wagner CA. Expression of NaPi-IIb in rodent and human kidney and upregulation in a model of chronic kidney disease. Pflugers Arch 2020; 472:449-460. [PMID: 32219532 DOI: 10.1007/s00424-020-02370-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 02/29/2020] [Accepted: 03/20/2020] [Indexed: 01/07/2023]
Abstract
Na+-coupled phosphate cotransporters from the SLC34 and SLC20 families of solute carriers mediate transepithelial transport of inorganic phosphate (Pi). NaPi-IIa/Slc34a1, NaPi-IIc/Slc34a3, and Pit-2/Slc20a2 are all expressed at the apical membrane of renal proximal tubules and therefore contribute to renal Pi reabsorption. Unlike NaPi-IIa and NaPi-IIc, which are rather kidney-specific, NaPi-IIb/Slc34a2 is expressed in several epithelial tissues, including the intestine, lung, testis, and mammary glands. Recently, the expression of NaPi-IIb was also reported in kidneys from rats fed on high Pi. Here, we systematically quantified the mRNA expression of SLC34 and SLC20 cotransporters in kidneys from mice, rats, and humans. In all three species, NaPi-IIa mRNA was by far the most abundant renal transcript. Low and comparable mRNA levels of the other four transporters, including NaPi-IIb, were detected in kidneys from rodents and humans. In mice, the renal expression of NaPi-IIa transcripts was restricted to the cortex, whereas NaPi-IIb mRNA was observed in medullary segments. Consistently, NaPi-IIb protein colocalized with uromodulin at the luminal membrane of thick ascending limbs of the loop of Henle segments. The abundance of NaPi-IIb transcripts in kidneys from mice was neither affected by dietary Pi, the absence of renal NaPi-IIc, nor the depletion of intestinal NaPi-IIb. In contrast, it was highly upregulated in a model of oxalate-induced kidney disease where all other SLC34 phosphate transporters were downregulated. Thus, NaPi-IIb may contribute to renal phosphate reabsorption, and its upregulation in kidney disease might promote hyperphosphatemia.
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Affiliation(s)
- Sarah E Motta
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Pedro Henrique Imenez Silva
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Arezoo Daryadel
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Betül Haykir
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Eva Maria Pastor-Arroyo
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
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Tenenhouse HS, Gauthier C, Martel J, Gesek FA, Coutermarsh BA, Friedman PA. Na+ -phosphate cotransport in mouse distal convoluted tubule cells: evidence for Glvr-1 and Ram-1 gene expression. J Bone Miner Res 1998; 13:590-7. [PMID: 9556059 DOI: 10.1359/jbmr.1998.13.4.590] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
While there is considerable evidence for phosphate (Pi) reabsorption in the distal tubule, Pi transport and its regulation have not been well characterized in this segment of the nephron. In the present study, we examined Na+-dependent Pi transport in immortalized mouse distal convoluted tubule (MDCT) cells. Pi uptake by MDCT cells is Na+-dependent and, under initial rate conditions, is inhibited by phosphonoformic acid (41 +/- 3% of control), a competitive inhibitor of Na+-Pi cotransport. The transport system has a high affinity for Pi (Km = 0.46 mM) and is stimulated by lowering the extracellular pH from 7.4 to 6.4 and inhibited by raising the pH from 7.4 to 8.4. Exposure to Pi-free medium for 21 h increased Na+-Pi cotransport from 2.1 to 5.5 nmol/mg of protein/5 minutes (p < 0.05) while parathyroid hormone, forskolin, and phorbol 12-myristate 13-acetate failed to alter Pi uptake in MDCT cells. Reverse transcriptase polymerase chain reaction of MDCT cell RNA provided evidence for the expression of the Npt1 but not the Npt2 Na+-Pi cotransporter gene. However, preincubation of MDCT cells with Npt1 antisense oligonucleotide led to only 20% inhibition of Na+-Pi cotransport, suggesting that other Na+-Pi cotransporters are operative in MDCT cells. Indeed, we showed, by ribonuclease protection assay, that MDCT cells express the ubiquitous cell surface receptors for gibbon ape leukemia virus (Glvr-1) and amphoteric murine retrovirus (Ram-1) that also function as Na+-Pi cotransporters. In summary, we demonstrate that the pH dependence and regulation of Na+-Pi cotransport in MDCT cells is distinct from that in the proximal tubule and suggest that different gene products mediate Na+-Pi cotransport in the proximal and distal segments of the nephron.
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Affiliation(s)
- H S Tenenhouse
- Department of Pediatrics, McGill University-Montreal Children's Hospital Research Institute, Quebec, Canada
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Good JM, Peters M, Wilkins M, Jackson N, Oakley CM, Cleland JG. Renal response to candoxatrilat in patients with heart failure. J Am Coll Cardiol 1995; 25:1273-81. [PMID: 7722120 DOI: 10.1016/0735-1097(94)00561-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVES Our primary objective was to compare the effects of three different doses of candoxatrilat with the effects of placebo on urinary volume in patients with moderately severe heart failure. The effects of candoxatrilat on urinary composition, neuroendocrine indexes and renal hemodynamic function were also studied. BACKGROUND Candoxatrilat, a neutral endopeptidase inhibitor, reduces degradation of atrial natriuretic peptide and provokes diuresis in patients with mild heart failure, but the renal effects have not been studied in patients with moderately severe heart failure in a placebo-controlled study. METHODS In a double-blind crossover trial, the effects of intravenous boluses of saline vehicle (placebo) and 50, 100 and 200 mg of candoxatrilat were compared on separate days in 12 patients with heart failure. Urinary output and composition were measured for 8 h. Renal blood flow and glomerular filtration rate were determined by radionuclide techniques. Blood was withdrawn for the measurement of hormones before and 3 h after dosing. RESULTS All doses of candoxatrilat increased urinary volume (e.g., [mean +/- SEM] 263 +/- 53 to 490 +/- 82 ml for saline solution and the 200-mg dose, respectively, p < 0.01) and sodium content (14 +/- 4 to 37 +/- 11 mmol, p < 0.001) in the 1st 4 h after dosing. Plasma atrial natriuretic peptide increased (140 +/- 26 to 279 +/- 37 pg/ml, p < 0.01), whereas aldosterone decreased (178 +/- 41 to 125 +/- 35 pg/ml, p < 0.01), and renin activity was unchanged (10 +/- 2 to 12 +/- 3 ng/ml per h). CONCLUSIONS Candoxatrilat given acutely causes diuresis, even in patients with moderately severe heart failure.
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Affiliation(s)
- J M Good
- Department of Medicine (Cardiology), Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom
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Kaskel FJ, Kumar AM, Feld LG, Spitzer A. Renal reabsorption of phosphate during development: tubular events. Pediatr Nephrol 1988; 2:129-34. [PMID: 3152986 DOI: 10.1007/bf00870393] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Studies performed in our laboratory on the isolated perfused kidney of the guinea pig have demonstrated that the rate of Pi reabsorption is substantially greater in the newborn than in the adult, when appropriate corrections are being made either for differences in glomerular filtration rate (GFR) or in renal tubular mass. In order to determine the location of this enhanced reabsorption along the nephron, micropuncture experiments were performed on euvolemic, non-fasted guinea pigs 5-14 and 42-49 days of age, maintained on standard guinea-pig chow diet (0.76% Pi). Concomitant measurements of overall kidney function were also obtained. The results confirmed that fractional reabsorption of Pi (TRPi%) across the entire kidney was significantly higher (P less than 0.01) in the newborn (89.93 +/- 2.55%) than in the adult (78.25 +/- 2.89%) animals. The difference was also significant (P less than 0.05) when TRPi was expressed in mol/ml GFR (1.87 +/- 0.14 vs 1.53 +/- 0.12, respectively). At comparable locations along the proximal tubule (TF/Pin of 1.90 +/- 0.16 in the newborn, and 1.79 +/- 0.15 in the adult, P greater than 0.70), the fraction of the filtered load of Pi reabsorbed was significantly higher (P less than 0.001) in the immature (76.66 +/- 2.74%) than in the mature (67.21 +/- 2.74%) guinea pigs. Estimates based on the differences between proximal Pi reabsorption and the urinary excretion of Pi indicate that the reabsorption of Pi in tubular segments located beyond the proximal tubule is also enhanced in the newborn when compared with the adult (15.62 +/- 2.11% vs 10.51 +/- 1.83%, respectively, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- F J Kaskel
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, NY 10461
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Kato S, Nakamura H. Ultracytochemical localization of alkaline phosphatase activity in endothelial cells in chronic relapsing experimental allergic encephalomyelitis. Acta Neuropathol 1987; 73:220-6. [PMID: 3618115 DOI: 10.1007/bf00686614] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
To investigate the functions of endothelial cells (ECs) in chronic relapsing experimental allergic encephalomyelitis (EAE), we examined ECs ultracytochemically in various stages of EAE, in conjunction with the localization of alkaline phosphatase (AP) activity. We also studied the relation between the specific localization of AP activity and pathological features at each stage. Chronic relapsing EAE was induced in strain-13 guinea pigs by inoculation with homologous myelin. Controls were inoculated with complete Freund's adjuvant. The controls showed AP activity on the luminal and abluminal surfaces of the plasmalemma, and in pinocytic vesicles and vesicular pits. The localization of AP activity in the preclinical stage of EAE was similar to that in control animals. The initial inflammatory and actively demyelinating stage with perivascular cuffs of mononuclear cells showed AP-positive reactions on the abluminal surface of the plasmalemma, and in vesicles and pits, but not on the luminal surface in many ECs. In a later stage showing relatively old plaques with perivascular accumulation of debris-containing macrophages, AP activity continued to show localization similar to that seen in the initial stage, except for the presence of AP activity on some segments of the abluminal plasmalemma. Inactive lesions with marked perivascular fibrosis showed no AP reaction products. AP activity in unaffected areas showed the same localization as that in control animals throughout the various clinical stages of EAE. These findings suggest that AP activity decreased as the inflammatory demyelination in EAE progressed. The gradual disappearance of AP activity suggests development of functional impairment of ECs.
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Lassiter WE, Colindres RE. Phosphate reabsorption in the distal convoluted tubule. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1982; 151:21-32. [PMID: 7180651 DOI: 10.1007/978-1-4684-4259-5_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Poujeol P, Jamison RL, de Rouffignac C. Phosphate reabsorption in juxtamedullary nephron terminal segments. Pflugers Arch 1980; 387:27-31. [PMID: 7191102 DOI: 10.1007/bf00580840] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Adult Munich Wistar rats undergoing mild salt diuresis (NaCl 20 g x l-1, 0.1 ml x min-1) were injected with tracer doses of 3H-Inulin and 32P-sodium phosphate in thin descending and ascending limbs of Henle's loop, collecting ducts accessible at the surface of the papilla and early distal superficial tubules. Kidneys were prepared for simultaneous papillar microinjection and urinary flow collection. Expressed in percent of the amounts injected, unidirectional phosphate reabsorption fluxes were 5 +/- 1% and 3 +/- 1% for injections into early distal superficial tubules and collecting ducts, respectively. By contrast, the flux was 21.7 +/- 3% for injections into either the descending or ascending thin limbs of juxtamedullary nephrons. We conclude from these results that in the rat, a significant amount of phosphate is reabsorbed by the juxtamedullary distal tubules and/or the subsequent arcades connecting the juxtamedullary distal tubules to the collecting ducts.
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Hay DA, Evan AP. Maturation of the proximal tubule in the puppy kidney: a comparison to the adult. Anat Rec (Hoboken) 1979; 195:273-99. [PMID: 507392 DOI: 10.1002/ar.1091950204] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Two- to four-day-old beagle puppy kidneys were preapred for transmission and scanning electron microscopy and compared to similarly prepared adult tissues. Proximal tubules of puppy kidneys which contained nephrons in various stages of differentiation were examined and maturational changes were described. Lateral surface contours of proximal tubular cells were initially smooth and relatively unfolded, but progressively acquired complex processes that may be recognized as lateral ridges and lateral-basal processes. Basal projections began as short, stubby processes and gradually took on either a narrow, plate-like or finger-like appearance. Mitochondria lysosomes and apical vacuoles increased in number as the tubules matured. Mitochondria lacked orientation in outer cortical tubules, but exhibited some vertical arrangement within basal processes in inner cortical tubules. Despite features indicating advanced maturation of tubules in the inner cortex, puppy kidneys lacked the lipid droplets characteristic of the adult. Thus, differentiation of this portion of the developing nephron into S1, S2 and S3 segments was not possible at day 4. Morphometric analyses of the lateral and basal membrane surface concentration of proximal convulted tubules from the puppy revealed all cells to have a significantly smaller membrane area than that of the adult. However, the inner cortical cells of the puppy had a greater surface concentration than those of the outer cortex. The reduced transport capacity of the puppy proximal tubule may be realted to the lack of segmentation and/or reduced lateral-basal surface area.
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Cowgill LD, Goldfarb S, Lau K, Slatopolsky E, Agus ZS. Evidence for an intrinsic renal tubular defect in mice with genetic hypophosphatemic rickets. J Clin Invest 1979; 63:1203-10. [PMID: 221535 PMCID: PMC372069 DOI: 10.1172/jci109415] [Citation(s) in RCA: 71] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
To investigate the role of parathyroid hormone (PTH) and(or) an intrinsic renal tubular reabsorptive defect for phosphate in mice with hereditary hypophosphatemic rickets, we performed clearance and micropuncture studies in hypophosphatemic mutants and nonaffected littermate controls. Increased fractional excretion of phosphate in mutants (47.2+/-4 vs. 30.8+/-2% in controls) was associated with reduced fractional and absolute reabsorption in the proximal convoluted tubule and more distal sites. Acute thyropara-thyroidectomy (TPTX) increased phosphate reabsorption in both mutants and controls with a fall in fractional phosphate excretion to congruent with7.5% in both groups indicating that PTH modified the degree of phosphaturia in the intact mutants. Absolute reabsorption in the proximal tubule and beyond remained reduced in the mutants, however, possibly because of the reduced filtered load. Serum PTH levels were the same in intact mutants and normals as was renal cortical adenylate cyclase activity both before and after PTH stimulation. To evaluate the possibility that the phosphate wasting was caused by an intrinsic tubular defect that was masked by TPTX, glomerular fluid phosphate concentration was raised by phosphate infusion in TPTX mutants to levels approaching those of control mice. Phosphate excretion rose markedly and fractional reabsorption fell, but there was no change in absolute phosphate reabsorption in either the proximal tubule or beyond, indicating a persistent reabsorptive defect in the absence of PTH. We conclude that hereditary hypophosphatemia in the mouse is associated with a renal tubular defect in phosphate reabsorption, which is independent of PTH and therefore represents a specific intrinsic abnormality of phosphate transport.
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Sellers BB, Hall JA, Mendoza SA. The role of cyclic AMP in parathyroid hormone action in the toad bladder. J Membr Biol 1978; 41:329-35. [PMID: 211236 DOI: 10.1007/bf01871997] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Parathyroid hormone (PTH) inhibited active transport of inorganic phosphate and stimulated an increase in cyclic AMP concentration in the urinary bladder of the toad, Bufo marinus. Active transport of phosphate in the toad bladder was also inhibited by an analog of cyclic AMP (dibutyryl cyclic AMP) and by other drugs (pitressin and theophylline) which increase toad bladder intracellular cyclic AMP concentration. These data support the concept that cyclic AMP may be the mediator of PTH-induced phosphate transport inhibition in the toad bladder.
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Bank N, Su WS, Aynedjian HS. A micropuncture study of renal phosphate transport in rats with chronic renal failure and secondary hyperparathyroidism. J Clin Invest 1978; 61:884-94. [PMID: 659581 PMCID: PMC372607 DOI: 10.1172/jci109014] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Micropuncture studies were carried out in rats to determine changes in tubular transport of phosphate which occur in chronic renal failure and secondary hyperparathyroidism. Rats underwent subtotal nephrectomy (NX) and were fed a low calcium, high phosphorus diet for 3--4 wk. Other groups consisted of normal control animals, normal rats infused with sodium phosphate to raise filtered load of phosphate, subtotal NX rats parathyroidectomized (PTX) on the day of experiment, and normal PTX rats infused with sodium phosphate. It was found that filtered phosphate/nephron is markedly increased in subtotal NX rats due to high single nephron filtration rates, proximal tubular fluid plasma phosphate ratios are less than 1.0, and fractional reabsorption of phosphate is decreased in the proximal tubule. More phosphate was present in the final urine than in surface distal convoluted tubules. Acute PTX in subtotal NX rats resulted in a striking increase in proximal phosphate reabsorption, and urinary phosphate became approximately equal to that remaining in surface distal tubules. Phosphate loading in normal rats reduced fractional reabsorption in the proximal tubule, but urinary phosphate was not greater than that at the end of surface distal tubules. Acute PTX in normal phosphate-loaded animals had no significant effect on proximal tubular phosphate reabsorption. These observations suggest that phosphate homeostasis in chronic renal failure is acheived by inhibition of proximal phosphate reabsorption, counteracting a greatly enhanced intrinsic capacity for reabsorption. In addition, the large amount of urinary phosphate is consistent either with secretion by the collecting ducts or with a disproportionately high contribution by deep nephrons. The changes in phosphate transport are mediated by parathyroid hormone and are completely abolished by acute removal of the hormone.
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Kuntziger H, Amiel C. Recent progress in renal handling of phosphate. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1978; 103:3-10. [PMID: 717110 DOI: 10.1007/978-1-4684-7758-0_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Poujeol P, Corman B, Touvay C, de Rouffignac C. Phosphate reabsorption in rat nephron terminal segments: intrarenal heterogeneity and strain differences. Pflugers Arch 1977; 371:39-44. [PMID: 563574 DOI: 10.1007/bf00580770] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Giasson SD, Brunette MG, Danan G, Vigneault N, Carriere S. Micropuncture study of renal phosphorus transport in hypophosphatemic vitamin D resistant rickets mice. Pflugers Arch 1977; 371:33-8. [PMID: 201919 DOI: 10.1007/bf00580769] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Webb RK, Woodhall PB, Tisher CC, Glaubiger G, Neelon FA, Robinson RR. Relationship between phosphaluria and acute hypercapnia in the rat. J Clin Invest 1977; 60:829-37. [PMID: 19498 PMCID: PMC372431 DOI: 10.1172/jci108837] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Standard clearance studies were performed in mechanically ventilated intact and acutely thyroparathyroidectomized (TPTX) rats to document and characterize the effect of hypercapnia (HC) on urinary phosphorus excretion (U(P)V). HC as compared to normocapnia (NC) was associated with an increase in U(P)V in intact (62.5 vs. 7.93 mug/min) and TPTX (30.5 vs. 0.59 mug/min) rats, an increase in filtered load of phosphorus in intact (218 vs. 191 mug/min) and TPTX (243 vs. 146 mug/min) rats, an increase in blood bicarbonate concentration in intact (27.8 vs. 26.0 meq/liter) and TPTX (24.5 vs. 22.3 meq/liter) animals, and a decrease in blood pH in intact (7.15 vs. 7.42) and TPTX (7.07 vs. 7.39) rats. Additional TPTX rats with NC and HC were studied during phosphorus infusion at a comparable filtered load of phosphorus (NC = 307 mug/min and HC = 328 mug/min). U(P)V was 18.5 mug/min in NC and 85.2 mug/min in HC animals. Intact NC animals infused with NaHCO(3) achieved a blood bicarbonate of 45.9 meq/liter compared to 26.0 meq/liter in intact NC NaCl-infused rats. U(P)V was 10.0 mug/min in the NaHCO(3) and 7.93 mug/min in NaCl-infused animals. In intact HC animals infused with NaHCO(3), blood pH was 7.36 compared to 7.42 in NC intact NaCl-infused animals. U(P)V was 83.2 mug/min in the HC bicarbonate-infused and 7.93 mug/min in the NC NaCl-infused rats. These experiments demonstrate that elevated blood carbon dioxide tension per se increases U(P)V. Increases in filtered load of phosphorus and blood bicarbonate which are associated with HC contribute to the phosphaturia as does parathyroid hormone. The phosphaturia is not dependent upon reduction of extracellular pH.
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Greger R, Lang F, Marchand G, Knox FG. Site of renal phosphate reabsorption. Micropuncture and microinfusion study. Pflugers Arch 1977; 369:111-8. [PMID: 560673 DOI: 10.1007/bf00591566] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Using modified microinfusion and free flow micropuncture techniques in the same intact and acutely thyroparathyroidectomized (TPTX) Munich-Wistar rats the nephron sites for phosphate reabsorption were reinvestigated. In intact animals, 62% of filtered phosphate was reabsorbed in the proximal tubule but none in the loop of Henle, here defined as the nephron segment between the last accessible proximal and the first distal convolution. Delivery of phosphate to the superficial distal tubule significantly exceeded urinary phosphate excretion but no phosphate reabsorption could be detected in the terminal nephron by distal microinfusions of radioactively labelled phosphate (32P). In TPTX rats, proximal phosphate reabsorption was enhanced and there was marked phosphate reabsorption in the loop of Henle. Similarly, 32P microinfused in the late proximal tubule was almost completely reabsorbed. Again, no phosphate tracer outflux was detected after distal microinfusion. It is concluded that phosphate reabsorption is confined to the proximal tubule and the loop of Henle.
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Sellers BB, Hall JA, Both CW, Mendoza SA. Active phosphate transport across the urinary bladder of the toad, Bufo marinus. J Membr Biol 1977; 32:291-9. [PMID: 405496 DOI: 10.1007/bf01905223] [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: 12/15/2022]
Abstract
Net transport of inorganic phosphate occurs in the absence of an electrochemical gradient from the mucosal to the serosal bathing solution in the isolated toad urinary bladder. This transport can be inhibited by metabolic inhibitors. The magnitude of this transport can be altered by changes in phosphate concentration or by the addition of parathyroid hormone.
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Lang F, Greger R, Marchand GR, Knox FG. Stationary microperfusion study of phosphate reabsorption in proximal and distal nephron segments. Pflugers Arch 1977; 368:45-8. [PMID: 558598 DOI: 10.1007/bf01063453] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Micropuncture studies demonstrate phosphate reabsorption in proximal tubules and between the late proximal and early distal convoluted tubule accessible to micropuncture. To further define the sites of phosphate reabsorption, the stationary microperfusion technique was applied to proximal and distal nephron segments. Phosphate reabsorption was evaluated in superficial loops of proximal tubules, descending segments beyound late proximal tubules accessible to micropuncture, ascending segments up to the point of micropuncture in the distal tubule, and superficial loops of distal tubules of thyroparathyroidectomized rats. Microperfusates of 1.3 or 2.6 nl (100 mmol/1 mannitol, 100 mmol/l NaCL, 32P-phosphate and 3H-inulin) were injected and then withdrawn after contact times of 2--108 s. Phosphate recovery relative to that of inulin was determined. A steep exponential decline of phosphate recovery (R) iwth increasing contact time (t) was observed in the superficial proximal tubule and descending segments. The slopes of the logarithmic regressions (10log R)/t, +/- SEM) were: -1.68 +/- 0.33 and -1.21 +/- 0.24min-1 in superficial proximal tubules and descending segments respectively. In contrast, no significant decline in phosphate recoveries (-0.02 +/- 0.04 and + 0.11 +/- 0.10 min-1) was apparent in the ascending segments and distal tubule. It is concluded that phosphate is reabsorbed in the proximal convoluted tubule and adjacent descending segments of the superficial nephron and that there is no significant phosphate reabsorption in distal convoluted tubules and adjacent ascending segments.
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Cassola AC, Malnic G. Phosphate transfer and tubular pH during renal stopped flow microperfusion experiments in the rat. Pflugers Arch 1977; 367:249-55. [PMID: 13346 DOI: 10.1007/bf00581362] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The loss of 32P-phosphate salts by the luminal compartment of cortical tubules was studied in control and in acetazolamide-infused rats, during stopped-flow microperfusion with 100 mM phosphate-raffinose solutions. When the initial pH of the perfusion solution was low (5.5), phosphate was lost more rapidly from proximal tubules than at high initial pH (8.2). The average half-time of phosphate loss was 31.9 s during acid, and 66.0 s during alkaline perfusion in proximal tubules of control rats; in acetazolamide-infused rats half-times were 77.0 and 86.6 s for acid and alkaline perfusions. Thus acetazolamide infusion slows the rate of phosphate loss by proximal tubules, when the perfusion solution is acid, but has no significant effect if its pH is alkaline. These half-times compare to proximal acidification rates of 7.23 s in control and 13.2 s in acetazolamide-infused rats. In distal tubules of control rats no significant loss of phosphate was observed during the period of perfusion. It is concluded that the loss of phosphate, in proximal tubules, is markedly slower than the changes in tubular pH and so its effect on tubular acidification must be of minor importance. In distal tubules changes in pH are not due to transepithelial phosphate movement.
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Knox FG, Greger RF, Lang FC, Marchand GR. Renal handling of phosphate: update. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1977; 81:3-14. [PMID: 19948 DOI: 10.1007/978-1-4613-4217-5_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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24
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Greger R, Lang F, Marchand G, Knox FG. The postproximal site of phosphate reabsorption in presence and absence of parathyroid hormone. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1977; 81:149-51. [PMID: 899924 DOI: 10.1007/978-1-4613-4217-5_17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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25
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Abstract
In order to determine the effects of guanabenz upon renal function, clearance studies were performed on hypertensive volunteers during sustained steady-state water diuresis. The data reveal an acute fall in renal hemodynamics and a marked reduction in sodium excretion during the 3rd and 4th hour after administration. Tha antinatriuresis was due to decreased filtration and enhanced distal nephron reabsorption of sodium, principally in association with secretion of potassium. Chronic administration of guanabenz for one week produced a sustained reduction in blood pressure, but there was no change in either body weight or 24-hour urinary sodium excretion. Repeat clearance studies revealed no change with either renal hemodynamics or sodium clearance. The data suggest that the acute antinatriuresis is a transient hemodynamic event and chronic therapy with guanabenz will not be complicated by sodium retention, a feature characteristic of other antihypertensive agents.
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Poujeol P, Chabardes D, Roinel N, De Rouffignac C. Influence of extracellular fluid volume expansion on magnesium, calcium and phosphate handling along the rat nephron. Pflugers Arch 1976; 365:203-11. [PMID: 988560 DOI: 10.1007/bf01067020] [Citation(s) in RCA: 43] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Renal tubular handling of P, Ca, Mg and Na was studied in the rat both before and during mild hypertonic NaCl loading (ECVE), using micropuncture and clearance techniques and electron microprobe analysis. Micropuncture was performed at the late proximal and early distal tubule sites. ECVE significantly increased the urinary output of all four elements. In the case of Mg, the increase was relatively small and depended on slight but statistically unsignificant inhibition of reabsorption all along the entire length of the nephron. For Ca, it depended on the inhibition of proximal reabsorption, partially compensated by increased reabsorption along the loop. For P, it depended on proximal inhibition, no important net phosphate movement occurring in the loop during both periods. Ca reabsorption was highly correlated to that of sodium along the proximal tubule and Henel's loop, Ca and Mg reabsorption were closely related to the load delivered at the beginning of the structure. These observations are compatible with the view that tubular reabsorption of Ca and Mg is concentration rather than Tm limited, and that reabsorption of Ca, unlike that of Mg, is linked to the movements of sodium. Following ECVE, the difference between early distal and urinary deliveries increased significantly for Ca and P, but not for Mg. For phosphate, this difference accounted for by 45% of the delivery at the early distal tubule site, at variance with microinjection data obtained in the rat under similar salt loading conditions, which indicated that 17% only of the phosphate distal delivery were reabsorbed along the terminal segments. This discrepancy is discussed in terms of nephron functional heterogeneity.
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27
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DeFronzo RA, Goldberg M, Agus ZS. The effects of glucose and insulin on renal electrolyte transport. J Clin Invest 1976; 58:83-90. [PMID: 932211 PMCID: PMC333158 DOI: 10.1172/jci108463] [Citation(s) in RCA: 320] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The effects of hyperglycemia and hyperinsulinemia on renal handling of sodium, calcium, and phosphate were studied in dogs employing the recollection micropuncture technique. Subthreshold sustained hyperglycemia resulted in an isonatric inhibition of proximal tubular sodium, fluid, calcium, and phosphate reabsorption by 8-14%. Fractional excretion of sodium and phosphate, however, fell (P is less than 0.01) indicating that the increased delivery of these ions was reabsorbed in portions of the nephron distal to the site of puncture and in addition net sodium and phosphate transport was enhanced resulting in a significant antinatriuresis and antiphosphaturia. The creation of a steady state plateau of hyperinsulinemia while maintaining the blood glucose concentration of euglycemic levels mimicked the effects of hyperglycemia on proximal tubular transport and fractional excretion of sodium and calcium. Tubular fluid to plasma insulin ratio fell, similar to the hyperglycemic studies. These results suggest that the effects of hyperglycemia on renal handling of sodium and calcium may be mediated through changes in plasma insulin concentration. In contrast to hyperglycemia, however, hyperinsulinemia cuased a significant fall in tubular fluid to plasma phosphate ratio with enhanced proximal tubular phosphate reabsorption (P is less than 0.02). This occurred concomitantly with a significant inhibition of proximal tubular sodium transport. These data indicate that insulin has a direct effect on proximal tubular phosphate reabsorption, and this effect of insulin is masked by the presence of increased amounts of unreabsorbed glucose in the tubule that ensues when hyperinsulinemia occurs secondary to hyperglycemia. Fractional excretion of phosphate fell significantly during insulin infusion but unlike the hyperglycemic studies, the fall in phosphate excretion could be entirely accounted for by enhanced proximal reabsorption.
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Bergeron M, Dubord L, Hausser C, Schwab C. Membrane permeability as a cause of transport defects in experimental Fanconi syndrome. A new hypothesis. J Clin Invest 1976; 57:1181-9. [PMID: 1262464 PMCID: PMC436771 DOI: 10.1172/jci108386] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The injection of sodium maleate (200-400 mg/kg) into rats produces aminoaciduria along with glycosuria and phosphaturia, resembling the Fanconi syndrome. This experimental model was studied by means of microinjections into proximal convoluted tubules of the kidney, stop-flow diuresis, and microperfusion of single nephrons. Our results show that, in maleate-treated rats, competition between amino acids or related structures (L-proline, L-OH-proline, and glycine) possesses the same characteristics, and net influx of amino acids appear normal at the proximal nephron. Data obtained by classical stop-flow techniques and single nephron microperfusions also indicate a normal entry of labeled amino acids (L-lysine, glycine, L-valine, L-proline, L-cystine), and 3-0-methyl-D-[3H]glucose and [32P]phosphate from the luminal side of the proximal tubule cell. However, the efflux of molecules from the cell appears enhanced throughout the proximal and distal tubule; molecules that exit at this site are excreted directly into the urine. Our results suggest that the phosphaturia, aminoaciduria, and glycosuria of the experimental Fanconi syndrome can be explained by a modification of the cell membrane permeability (increased efflux) at distal sites of the nephron rather than by a modification of the membrane transport (decreased influx) at the proximal sites, as is currently accepted. Our data also stress the importance of efflux phenomena in membrane transport.
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Baumann K, de Rouffignac C, Roinel N, Rumrich G, Ullrich KJ. Renal phosphate transport: inhomogeneity of local proximal transport rates and sodium dependence. Pflugers Arch 1975; 356:287-98. [PMID: 1171445 DOI: 10.1007/bf00580003] [Citation(s) in RCA: 90] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The standing droplet method has been used in combination with the peritibular perfusion of blood capillaries to determine the build up of transtubular concentration differences of phosphate (Piota) in the renal proximal convoluted tubule of parathyroidectomized rats. Electron probe analysis was used to estimate Piota. At zero time both the intraluminal and the contraluminal Piota concentration was 2 mM. The time dependent decrease of the intraluminal Piota concentration was approximately 4 times faster in the early than in the late proximal convoluted tubule. After 45 sec an intraluminal steady state concentration of 0.20 mM Piota was achieved in the early part. In the late part the intraluminal Piota concentration approached a steady statevalue of 0.54 mM at 123 sec. When sodium free solutions were used the intaluminal Piota concentration increased to 2.22 mM in the earlier and to 2.76 mM in the late part. The data indicate that in the proximal convoluted tubule 1. the rate of phosphate reabsorption is greater in the early part than in the later part, and 2. phospate reabsorption might occur as co-transport with Na+ ions.
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30
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Baumann K, Rumrich G, Papavassiliou F, Klöss S. Letter: pH dependence of phosphate reabsorption in the proximal tubule of rat kidney. Pflugers Arch 1975; 360:183-7. [PMID: 241974 DOI: 10.1007/bf00580540] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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31
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Weinman EJ, Eknoyan G, Suki WN. The influence of the extracellular fluid volume on the tubular reabsorption of uric acid. J Clin Invest 1975; 55:283-91. [PMID: 1127100 PMCID: PMC301746 DOI: 10.1172/jci107931] [Citation(s) in RCA: 75] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Changes is tubular reabsorption of uric acid in response to alterations in the extracellular fluid volume (ECFV) were examined in rats by clearance studies and by direct intratubular microinjections. Contraction of the ECFV led to a rise in the serum uric acid concentration and a 47% decrease in the clearance of uric acid. The ratio of uric acid to inulin clearance also fell, indicating an increase in the net tubular reabsorption of urate. Volume expansion resulted in an increase in the urate clearance and a 37% decrease in the net tubular reabsorption of uric acid. To localize the site in the nephron where these changes occur, microinjections of [2-14C]urate were performed. The lack of conversion of radioactive urate to allantoin after microinjections was demonstrated by thin-layer chromatography. After contraction of the ECFV, urinary recoveries of uric acid were significantly decreased after microinjections into proximal tubular sites. In contrast, recoveries were increased from these proximal sites after volume expansion. No evidence for distral reabsorption was obtained in any group of animals. These studies demonstrate that net urate reabsorption is influenced by the state of hydration of the ECFV and that these alterations are mediated by changes in the rates of reabsorption in the proximal tubule.
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Lingard JM, Györy AZ, Young JA. Microperfusion study of the kinetics of reabsorption of cycloleucine in early and late segments of the proximal convolution of the rat nephron. Pflugers Arch 1975; 357:51-61. [PMID: 239388 DOI: 10.1007/bf00584544] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The proximal tubular reabsorptive capacity for the non-metabolizable amino acid, cycloleucine, was studied in the rat nephron by stationary microperfusion. Tubular reabsorptive rates were greatest near the glomerulus and declined progressively along the convolution. A kinetic analysis of cycloleucine reabsorption in terms of luminal concentration revealed that this reduced transport rate was associated with an increase in the half-saturation constant of the kinetic curve, rather than a decrease in the maximum transport capacity. Since our previous findings with the metabolizable amino acid, -L-histidine, were identical we can conclude that this decline in reabsorption of neutral amino acids as a function of distance along the convolution is an intrinsic property of the transport system and is not related to tubule cell amino acid metabolism. The transport curves for cycloleucine absorption did not give a simple Michaelis-Menten relation but rather followed a course suggesting that more than one transport system might be involved.
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Bank N, Aynedjian HS, Weinstein SW. A microperfusion study of phosphate reabsorption by the rat proximal renal tubule. Effect of parathyroid hormone. J Clin Invest 1974; 54:1040-8. [PMID: 4418449 PMCID: PMC301651 DOI: 10.1172/jci107847] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
To study the mechanism of phsophate reabsorption by the proximal tubule and the effect of parathyroid hormone (PTH), microperfusion experiments were carried out in rats. Segments of proximal tubule isolated by oil blocks were perfused in vivo with one of three solutions, each containing 152 meq/liter Na(+) and 2 mmol/liter phosphate, but otherwise differing in composition. The pH of solution 1 was 6.05-6.63, indicating that 60-85% of the phosphate was in the form of H(2)PO(4) (-). The pH of solution 2 was 7.56-7.85, and 85-92% of the phosphate was in the form of HPO(4) (=). Solution 3 contained HCO(3) (-) and glucose and had a pH of 7.50-7.65. When the proximal tubules were perfused with solution 1, the (32)P concentration in the collected perfusate was found to be consistently lower than in the initial perfusion solution. In sharp contrast, when the tubules were perfused with solutions 2 or 3, (32)P concentration usually rose above that in the initial solution. Water (and persumably Na(+)) reabsorption, as measured with [(3)H]inulin, was the same with the acid and alkaline solutions. Administration of partially purified PTH clearly prevented the fall in phosphate concentration with the acid solution, but had a less discernible effect on phosphate reabsorption with the two alkaline solutions. Measurements of pH within the perfused segments with antimony microelectrodes demonstrated that PTH enhanced alkalinization of the acid perfusion solution. The findings are consistent with the view that H(2)PO(4) (-) is reabsorbed preferentially over HPO(4) (=). This can be attributed to either an active transport mechanism for H(2)PO(4) (-) or selective membrane permeability to this anion. PTH appears to either inhibit an active transport process for H(2)PO(4) (-), or to interfere with passive diffusion of phosphate by alkalinizing the tubular lumen.
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35
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Le Grimellec C, Roinel N, Morel F. Simultaneous Mg, Ca, P, K and Cl analysis in rat tubular fluid. IV. During acute phosphate plasma loading. Pflugers Arch 1974; 346:189-204. [PMID: 4856413 DOI: 10.1007/bf00595706] [Citation(s) in RCA: 39] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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36
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Györy AZ, Lingard JM, Young JA. Relation between active sodium transport and distance along the proximal convolutions of rat nephrons: evidence for homogeneity of sodium transport. Pflugers Arch 1974; 348:205-10. [PMID: 4857962 DOI: 10.1007/bf00587411] [Citation(s) in RCA: 16] [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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37
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Puschett JB, Beck WS, Jelonek A, Fernandez PC. Study of the renal tubular interactions of thyrocalcitonin, cyclic adenosine 3',5'-monophosphate, 25-hydroxycholecalciferol, and calcium ion. J Clin Invest 1974; 53:756-67. [PMID: 4359939 PMCID: PMC333056 DOI: 10.1172/jci107614] [Citation(s) in RCA: 46] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Acute clearance studies were performed in thyroparathyroidectomized animals to determine the actions and interactions of thyrocalcitonin (TCT), cyclic adenosine 3'5'-monophosphate (cAMP), 25-hydroxycholecalciferol (25HCC), and calcium ion on the reabsorption of phosphate, calcium, sodium, and potassium by the kidney. The infusion of 25HCC in a dosage of 60 U/h to moderately saline-expanded animals (2.5% body weight) induced a fall in the excretion of all of the ions under study after 90-120 min similar to that observed in previous experiments from this laboratory. Mean decrements in fractional excretion were: phosphate, 42.0% (P < 0.005); calcium, 25.0% (P < 0.005); sodium, 23.4% (P < 0.001); and potassium, 14.7% (P < 0.005). The superimposition of either porcine or salmon TCT (1-100 MRC U/h for 2 h) resulted in no further alterations in electrolyte excretion. However, the infusion of TCT during steady-state saline expansion, before the administration of 25HCC, obviated the renal transport effects of the vitamin D metabolite. Both in the latter studies, as well as those in which similar doses of TCT were given to hydropenic animals, the hormone itself failed to induce any consistent alteration in electrolyte excretion. Cyclic AMP (50 mg/h) caused an increase in the excretion of phosphate, sodium, and potassium and no change in calcium excretion. Like TCT, the nucleotide blocked the action of 25HCC on the kidney. Raising the mean level of serum ultrafilterable calcium to 3.02+/-0.25 mEq/liter from 1.62+/-0.17 mEq/liter likewise prevented enhanced ionic reabsorption due to 25HCC.
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38
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Wen SF. Micropuncture studies of phosphate transport in the proximal tubule of the dog. The relationship to sodium reabsorption. J Clin Invest 1974; 53:143-53. [PMID: 4808634 PMCID: PMC301448 DOI: 10.1172/jci107532] [Citation(s) in RCA: 73] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Micropuncture studies were performed in the dog to examine the relationship between sodium and phosphate transport in the proximal tubule. In hydropenic, thyroparathyroidectomized animals, administration of parathyroid extract, saline, or acetazolamide resulted in a fall in proximal tubule fluid-to-plasma (TF/P) inulin ratio as well as a rise in tubule fluid-to-plasma ultrafilterable (TF/UF) phosphate ratio. A correlation was found between the changes in fractional reabsorption of sodium and phosphate but the phosphate changes were generally greater than those of sodium. Also, a high distal phosphate delivery in the face of low fractional excretion of phosphate in the urine in thyroparathyroidectomized dogs suggests significant phosphate reabsorption in the distal nephron. On the other hand, calcium chloride infusion to saline-loaded, normal dogs to suppress endogenous parathyroid hormone reduced proximal TF/UF phosphate without change in TF/P inulin, while both parameters remained unchanged in saline-loaded, thyroparathyroidectomized dogs after calcium infusion. An increase in proximal TF/UF phosphate associated with unchanged TF/P inulin was also demonstrated by administration of highly purified parathyroid hormone to saline-loaded, thyroparathyroidectomized dogs. It was concluded that although proximal tubule phosphate transport is generally closely related to that of sodium, the two can dissociate under certain experimental conditions, especially under the influence of parathyroid hormone. These observations also indicate that the effect of parathyroid hormone on proximal tubule phosphate transport is not solely dependent upon its effect on sodium transport.
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39
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Schneider EG, Strandhoy JW, Willis LR, Knox FG. Relationship between proximal sodium reabsorption and excretion of calcium, magnesium and phosphate. Kidney Int 1973; 4:369-76. [PMID: 4780266 DOI: 10.1038/ki.1973.133] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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40
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de Rouffignac C, Morel F, Moss N, Roinel N. Micropuncture study of water and electrolyte movements along the loop of Henle in psammomys with special reference to magnesium, calcium and phosphorus. Pflugers Arch 1973; 344:309-26. [PMID: 4798168 DOI: 10.1007/bf00592784] [Citation(s) in RCA: 78] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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41
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Slatopolsky E, Bricker NS. The role of phosphorus restriction in the prevention of secondary hyperparathyroidism in chronic renal disease. Kidney Int 1973; 4:141-5. [PMID: 4355426 DOI: 10.1038/ki.1973.92] [Citation(s) in RCA: 173] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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42
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Knox FG, Schneider EG, Willis LR, Strandhoy JW, Ott CE. Effect of volume expansion on sodium excretion in the presence and absence of increased delivery from superficial proximal tubules. J Clin Invest 1973; 52:1642-6. [PMID: 4718957 PMCID: PMC302438 DOI: 10.1172/jci107344] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The role of the proximal tubule in the natriuresis after volume expansion was investigated by evaluating sodium excretion both in the presence and absence of increased delivery from the proximal tubule. Proximal delivery was calculated from fractional reabsorption in superficial proximal tubules determined by micropuncture and glomerular filtration rate of the micropunctured kidney. Infusion of Ringer's solution in six dogs increased delivery from the proximal tubule 4.7+/-1 ml/min (P < 0.01) and increased fractional sodium excretion 3.6+/-1.1% (P < 0.025). Infusion of hyperoncotic albumin into the renal artery during sustained volume expansion decreased delivery from the proximal tubule 6.5+/-0.9 ml/min (P < 0.01). Although proximal delivery was restored to below control levels, fractional sodium excretion was significantly increased 2.5+/-0.5% (P < 0.01) as compared with the hydropenic control period. Fractional phosphate excretion was increased 15.5+/-3.7% (P < 0.01) after Ringer's infusion and was decreased 10.5+/-1.6% (P < 0.005) after intrarenal albumin infusion, suggesting that changes in superficial nephron reabsorption were paralleled by changes in reabsorption in deeper nephrons. Similar results were found in six additional dogs in which other factors known to affect phosphate reabsorption were controlled; however, these studies cannot completely eliminate a role for deep nephrons in the natriuresis after intrarenal albumin infusion. Since 70% of the natriuresis after volume expansion was present without increased delivery from superficial proximal tubules, it is likely that increased delivery from the proximal tubule contributes a relatively minor fraction to the natriuresis of volume expansion.
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Knox FG, Schneider EG, Willis LR, Strandhoy JW, Ott CE. Editorial: Site and control of phosphate reabsorption by the kidney. Kidney Int 1973; 3:347-53. [PMID: 4791139 DOI: 10.1038/ki.1973.56] [Citation(s) in RCA: 47] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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