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  • 1
    Electronic Resource
    Electronic Resource
    Stimulation by glucagon and PTH of Ca and Mg reabsorption in the superficial distal tubule of the rat kidney (1985)
    Springer
    Pflügers Archiv 403 (1985), S. 28-34 
    Details
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of glucagon and PTH on electrolyte reabsorption in the distal tubule were investigated in rats deprived of vasopressin, calcitonin, PTH, and glucagon. Micropunctures of distal tubule, at a late and an early site of a same nephron, have been performed in 23 rats, nine control, seven infused with glucagon (5 ng·min−1·100 g−1 b.w.) and seven with PTH (5 mU·min−1·100 g−1 b.w.). The Ca and Mg reabsorptive capacity of the distal segment was increased by glucagon and by PTH. Moreover, fractional Na and Cl reabsorption was significantly higher than in control during PTH administration. A K secretion appeared during the administration of both hormones. No phosphate net transport was observed in any group. Finally, the data presented here, together with those previously reported, indicate that the increase of Ca and Mg renal reabsorption observed with glucagon and PTH results from an effect located in both Henle's loop, where the bulk of Ca and Mg is reabsorbed, and the distal tubule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583277
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  • 2
    Electronic Resource
    Electronic Resource
    Differential effects of ADH on sodium, chloride, potassium, calcium and magnesium transport in cortical and medullary thick ascending limbs of mouse nephron (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 516-523 
    Details
    ISSN: 1432-2013
    Keywords: ADH ; Transepithelial ion net fluxes ; Na+, Cl−, K+, Ca2+ and Mg2+ transport ; Electron microprobe ; Mouse kidney ; Cortical and medullary thick ascending limb of Henle's loop ; In vitro microperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of antidiuretic hormone (arginine vasopressin, AVP) on transepithelial Na+, Cl−, K+, Ca2+ and Mg2+ net transports was investigated in medullary (mTAL) and cortical (cTAL) segments of the thick ascending limb (TAL) of mouse nephron, perfused in vitro. Transepithelial net fluxes (J Na +,J Cl −,J K +,J Ca 2+,J Mg 2+) were determined by electron probe analysis of the collected tubular fluid. Transepithelial potential difference (PDte) and transepithelial resistance (Rte) were measured simultaneously. cTAL segments were bathed and perfused with isoosmolal, HCO 3 − containing Ringer solutions, mTAL segments were bathed and perfused with isoosmolal HCO 3 − free Ringer solutions. In cTAL segments, AVP (10−10 mol·l−1) significantly increasedJ Mg 2+ andJ Ca 2+ from 0.39±0.08 to 0.58±0.10 and from 0.86±0.13 to 1.19±0.15 pmol·min−1 mm−1 respectively. NeitherJ Na + norJ Cl −, (J Na +: 213±30 versus 221±28 pmol·min−1 mm−1,J Cl −: 206±30 versus 220±23 pmol·min−1 mm−1) nor PDte (13.4±1.3 mV versus 14.1±1.9 mV) or Rte (24.6±6.5Ω cm2 versus 22.6±6.4Ω cm2) were significantly changed by AVP. No significant effect of AVP on net K+ transport was observed. In mTAL segments, Mg2+ and Ca2+ net transports were close to zero and AVP (10−10 mol·l−1) elicited no effect. However NaCl net reabsorption was significantly stimulated by the hormone,J Na + increased from 107±33 to 148±30 andJ Cl − from 121±33 to 165±32 pmol·min−1 mm−1. The rise inJ NaCl was accompanied by an increase in PDte from 9.0±0.7 to 13.5±0.9 mV and a decrease in Rte from 14.4±2.0 to 11.2±1.7 Ω cm2. No K+ net transport was detected, either under control conditions or in the presence of AVP. To test for a possible effect of HCO 3 − on transepithelial ion fluxes, mTAL segments were bathed and perfused with HCO 3 − containing Ringer solutions. With the exception ofJ Ca 2+ which was significantly different from zero (J Ca 2+: 0.26±0.06 pmol·min−1 mm−1), net transepithelial fluxes of Na+, Cl−, K+ and Mg2+ were unaffected by HCO 3 − . In the presence of AVP,J Mg 2+ andJ Ca 2+ were unaltered whereasJ NaCl was stimulated to the same extent as observed in the absence of HCO 3 − . In conclusion our results indicate heterogeneity of response to AVP in cortical and medullary segments of the TAL segment, since AVP stimulates Ca2+ and Mg2+ reabsorption in the cortical part and Na+ and Cl− reabsorption in the medullary part of this nephron segment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582541
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  • 3
    Electronic Resource
    Electronic Resource
    Magnesium handling in the dog kidney: A micropuncture study (1978)
    Springer
    Pflügers Archiv 377 (1978), S. 95-99 
    Details
    ISSN: 1432-2013
    Keywords: Micropuncture ; Dog ; Mg, Ca, Na, K, Pi reabsorption ; Electron probe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Micropuncture and clearance experiments were done on normal dogs to investigate magnesium handling by proximal and distal nephron segments. Tubular fluid electrolytes were analyzed with the electron microprobe. Tubular fluid to ultrafilterable magnesium ratio (TF/UF magnesium) was observed to rise above unity but less than the TF/P inulin ratio generated along the proximal tubule. This is in contrast to the other major cations, the ratios of which remain close to unity as water is abstracted. Tubular fluid obtained from the distal tubule contained less magnesium than the glomerular filtrate (mean TF/UF magnesium of 0.6) indicating the loop of Henle is the major nephron segment reclaiming a significant portion of the filtered load. The faction of filtered load remaining at the distal sampling site was similar to the fraction appearing in the urine (8% vs 7%) indicating very little reabsorption beyond the distal tubule in these normal states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584380
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  • 4
    Electronic Resource
    Electronic Resource
    Renal phosphate transport: Inhomogeneity of local proximal transport rates and sodium dependence (1975)
    Springer
    Pflügers Archiv 356 (1975), S. 287-297 
    Details
    ISSN: 1432-2013
    Keywords: Renal Tubule ; Phosphate Transport ; Sodium Dependence ; Micropuncture ; Microperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The standing droplet method has been used in combination with the peritubular perfusion of blood capillaries to determine the build up of transtubular concentration differences of phosphate (P i ) in the renal proximal convoluted tubule of parathyroidectomized rats. Electron probe analysis was used to estimate P i . At zero time both the intraluminal and the contraluminal P i concentration was 2 mM. The time dependent decrease of the intraluminal P i 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 P i was achieved in the early part. In the late part the intraluminal P i concentration approached a steady state value of 0.54 mM at 120 sec. When sodium free solutions were used the intraluminal P i 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. phosphate reabsorption might occur as co-transport with Na+ ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580003
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of extracellular fluid volume expansion on magnesium, calcium and phosphate handling along the rat nephron (1976)
    Springer
    Pflügers Archiv 365 (1976), S. 203-211 
    Details
    ISSN: 1432-2013
    Keywords: Extracellular fluid volume expansion ; Mg, Ca and Pi renal handling ; Electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 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 dependend 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 occuring in the loop during both periods. Ca reabsorption was highly correlated to that of sodium along the proximal tubule and Henle's loop. This was not the case for Mg and P. In the 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067020
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  • 6
    Electronic Resource
    Electronic Resource
    Micropuncture study of water and electrolyte movements along the loop of henle in Psammomys with special reference to magnesium, calcium and phosphorus (1973)
    Springer
    Pflügers Archiv 344 (1973), S. 309-326 
    Details
    ISSN: 1432-2013
    Keywords: Micropuncture ; Mg, Ca and P Excretion ; Concentrating Mechanism ; Loop of Henle ; Electron Probe Analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cortical and papillary micropuncture experiments were carried out on Psammomys undergoing mild hypertonic salt diuresis. Tubular fluid was collected along the proximal tubule or at the early distal tubule level, and at the tip of the longest Henle loop.3H-inulin, Na, K, Cl, Mg, Ca and P concentrations, as well as osmotic pressure, were determined in all samples. The results indicate a) no large net water movement along the loop; b) substantial addition of Na, K, Cl, Mg, and to a lesser extent Ca, along the descending limb, in proportion to the gradient; c) the tubular flow rate of phosphorus remains constant at the tip of the loop irrespective of the gradient. The constancy of the load of Na, K, Cl, Mg and Ca delivered to the distal superficial nephron, irrespective of the urinary osmotic pressure, indicates that medullary recycling between the ascending and descending limbs exists for Mg, Cl, and Ca, and confirms its existence for Na and K. In contrast, phosphorus behaves like inulin along the descending limb. A general conclusion is that in Psammomys the concentrating process along the descending limb of Henle results mainly from net addition of solutes, and not from water withdrawal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592784
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  • 7
    Electronic Resource
    Electronic Resource
    Glucagon inhibits water and NaCl transports in the proximal convoluted tubule of the rat kidney (1991)
    Springer
    Pflügers Archiv 419 (1991), S. 472-477 
    Details
    ISSN: 1432-2013
    Keywords: Glucagon ; Transepithelial ion net fluxes ; Water, Na+, Cl−, K+, Mg2+, Ca2+, transport ; Electron microprobe ; Rat kidney ; In vivo micropuncture study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of glucagon on water and electrolyte transport in the kidney were investigated on hormone-deprived rats, i.e. thyroparathyroidectomized diabetes insipidus Brattleboro rats infused with somatostatin. Glucagon consistently inhibited the reabsorption of water and Na+, Cl−, K+ and Ca2+ along the proximal tubule accessible to micropuncture, leaving the reabsorption of inorganic phosphate (Pi) untouched. In the loop, besides its previously described stimulatory effects on Na+, Cl−, K+, Ca2+ and Mg2+ reabsorption, glucagon strongly inhibited Pi reabsorption, very probably in the proximal straight tubule. These effects resulted in a significant phosphaturia and considerable reductions of Mg2+ and Ca2+ excretions. The effects of glucagon at both the whole kidney and the nephron levels are very similar to those previously described for calcitonin. In the absence of an adenylate cyclase system sensitive to glucagon and calcitonin in the rat proximal tubule, and from the analogy of their physiological effects with those elicited by parathyroid hormone, it is suggested that glucagon and calcitonin exert their inhibitory effects on Na and Pi reabsorption in the proximal tubule through another pathway, which could be the phosphoinositide regulatory cascade.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370791
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  • 8
    Electronic Resource
    Electronic Resource
    Stimulation of NaCl reabsorption by antidiuretic hormone in the cortical thick ascending limb of Henle's loop of the mouse (1991)
    Springer
    Pflügers Archiv 419 (1991), S. 212-214 
    Details
    ISSN: 1432-2013
    Keywords: ADH ; Mouse nephron ; Microperfusion ; NaCl transport ; Mg2+ transport ; Ca2+ transport ; Electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of antidiuretic hormone (ADH) on transepithelial Na+, Cl−, Ca2+ and Mg2+ net fluxes (JNa, JCl, JMg, JCa) was investigated in isolated perfused cortical thick ascending limb segments (cTAL) of the mouse nephron, using the microperfusion technique and the electron microprobe analysis to determine the ionic composition of the collected tubular fluid. Simultaneously, the transepithelial potential difference (PDte) and the transepithelial resistance (Rte) were recorded. Prior to the flux measurements cTAL segments were perfused for one hour. During this equilibration period PDte decreased significantly from +19.9±1.6 to +14.9±1.l mV and Rte increased from 30.6±3.5 Ωcm2 to 38.8±2.4 Ωcm2 (n=7), reflecting a decline in NaCl transport. After ADH was added to the bath solution at 10−10 mol.l−1, PDte increased from +14.4±1.1 to +18.0±1.5 mV, accompanied by a rise in JNa and JCl from 205±11 to 273±19 and from 216±12 to 283±21 pmol.min−1.mm−1 (n=7), respectively. JCa and JMg also increased from 0.81±0.07 to 1.50±0.12 and from 0.43±0.11 to 0.76±0.08 pmol.min−1.mm−1 (n=7), respectively. All these effects were fully reversible after withdrawal of the hormone. In conclusion our data indicate that ADH stimulates divalent cation transport and NaCl transport in the cortical thick ascending limb of Henle's loop of the mouse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373010
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of parathyroid hormone and calcitonin on Na+, Cl−, K+, Mg2+ and Ca2+ transport in cortical and medullary thick ascending limbs of mouse kidney (1990)
    Springer
    Pflügers Archiv 417 (1990), S. 161-167 
    Details
    ISSN: 1432-2013
    Keywords: Parathyroid hormone ; Human calcitonin ; Transepithelial ion net fluxes ; Na+, Cl−, K+, Mg2+, Ca2+ transport ; Electron microprobe analysis-Mouse kidney ; In vitro microperfusion ; Cortical and medullary thick ascending limb of Henle's loop
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of parathyroid hormone (PTH) on transepithelial Na+, Cl−, K+, Ca2+ and Mg2+ transport was investigated in isolated perfused cortical thick ascending limbs (cTAL) and that of human calcitonin (hCT) was tested in both cortical and medullary thick ascending limbs (mTAL) of the mouse nephron. The transepithelial ion net fluxes (J x) were determined by electron probe analysis of the perfused and collected fluids. Simultaneously, the transepithelial voltage (PDte) and resistance (R te) were recorded. In cTAL segments, PTH and hCT significantly stimulated the reabsorption of Na+, Cl−, Ca2+ and Mg2+. hCT generated a net K+ secretion towards the lumen and PTH tended to exert the same effect. Neither PDte nor R te were significantly altered by either PTH or hCT. However, in the post-experimental period a significant decrease in PDte was noted. Time control experiments carried out under similar conditions revealed a significant decrease in PDte with time, which could have masked the hormonal response. In mTAL segments, Mg2+ and Ca2+ transport was close to zero. hCT did not exert any detectable effect on either PDte or J Cl −, J Na + J K +, J Mg 2+ and J Ca 2+ in these segments. In conclusion, our data demonstrate that PTH and hCT stimulate NaCl reabsorption as well as Mg2+ and Ca2+ reabsorption in the cTAL segment of the mouse. These data are in agreement with and extend data obtained in vivo in the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370694
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  • 10
    Electronic Resource
    Electronic Resource
    Ca2+, Mg2+ and K+ transport in the cortical and medullary thick ascending limb of the rat nephron: influence of transepithelial voltage (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 558-560 
    Details
    ISSN: 1432-2013
    Keywords: Isolated thick ascending limb ; Microperfusion ; Divalent cation and potassium transport ; Microprobe analysis ; Transepithelial voltage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Isolated segments of rat cortical (cTAL) and medullary (mTAL) thick ascending limbs were microperfused and the transepithelial net fluxes (Jx) were determined by measuring the composition of the collected fluid with an electron microprobe. When perfused with symmetrical solutions both segments showed similar JNa and jCl and lumen-positive transepithelial voltage (V te=7–8 mV). JMg, JCa and JK were not significantly different from zero. When perfused with asymmetrical solutions (lumen 50 mM, bath 150 mM NaCl), the mean Vte were 23 mV and 17 mV in the cTAL and mTAL respectively; this rise was accompanied by significant increases in JMg and JCa in the cTAL, but not in the mTAL, and a marked increase in JK in both segments. It is concluded that, in the rat, divalent cations can be reabsorbed in the cTAL, and K+ can be reabsorbed in the cTAL and mTAL. The transport is voltage-dependent. The mTAL can reabsorb neither Mg2+ nor Ca2+, whatever Vte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374924
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