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  • 1
    Electronic Resource
    Electronic Resource
    The structural organization of the kidney of the desert rodent Psammomys obesus (1975)
    Springer
    Anatomy and embryology 148 (1975), S. 121-143 
    Details
    ISSN: 1432-0568
    Keywords: Psammomys kidney ; Renal architecture ; Short-looped nephrons ; Long-looped nephrons ; Renal pelvis ; Urea recycling possibilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The architecture of the desert rodent Psammomys obesus has been studied by means of standard histologic procedures and by single nephron injections. As other rodent kidneys (rat, mouse), the Psammomys kidney consists of two types of nephrons, 66% short looped and 34% long looped nephrons. The cortex is composed of 4 to 5 layers of glomeruli, which lie closely put together, the glomeruli often touch each other. The superficial and the midcortical glomeruli give rise to short looped nephrons, the juxtamedullary to long looped nephrons. In the strongly developed medulla the inner stripe shows the most striking pattern. It consists of two distinct compartements, that of the giant vascular bundles and that of the interbundle regions. The giant vascular bundles consist of about 8 to 14% arterial vasa recta and 39 to 47% venous vasa recta; furthermore they include the thin descending limbs of the short loops of Henle which amount to 44 to 51% of the bundle structures. The tubules of the interbundle regions surround the bundles in a regular pattern. The inner zone is almost completely surrounded by the renal pelvis; the long broad papilla protrudes into the ureter. The thin descending limbs of short looped nephrons traverse the inner stripe inside the giant vascular bundles. Leaving the bundles they turn back within the inner stripe; their ascending limbs lie in the interbundle region. Both limbs of the long loops of Henle run in the interbundle region, together with the ascending limbs of the short loops and the collecting ducts. The long loops penetrate deeply the inner zone. Many bends are found near the tip of the papilla. The renal pelvis has a very specialized form. It penetrates the inner stripe with many complexely shaped extensions, which surround the giant vascular bundles. Large parts of the bundles with their thin walled structures are thus separated from the pelvic urine only by a single layer of cuboidal epithelium. The possible functional importance of the described specializations of the Psammomys kidney (giant vascular bundles, large inner zone, special shape of the renal pelvis) for the urine concentrating and urea recycling mechanisms is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315265
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium and Magnesium: Low Passive Permeability and Tubular Secretion in the Mouse Medullary Thick Ascending Limb of Henle's Loop (MTAL) (1996)
    Springer
    The journal of membrane biology 153 (1996), S. 27-35 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Medullary thick ascending limb — Ca2+ transport — Mg2+ transport — Electron microprobe analysis — Passive permeability — ADH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Recent studies from our laboratory have shown that in the mouse and rat nephron Ca2+ and Mg2+ are not reabsorbed in the medullary part of the thick ascending limb (mTAL) of Henle's loop. The aim of the present study was to investigate whether the absence of transepithelial Ca2+ and Mg2+ transport in the mouse mTAL is due to its relative low permeability to divalent cations. For this purpose, transepithelial ion net fluxes were measured by electron probe analysis in isolated perfused mouse mTAL segments, when the transepithelial potential difference (PDte.) was varied by chemical voltage clamp, during active NaCl transport inhibition by luminal furosemide. The results show that transepithelial Ca2+ and Mg2+ net fluxes in the mTAL are not driven by the transepithelial PDte. At zero voltage, a small but significant net secretion of Ca2+ into the tubular lumen was observed. With a high lumen-positive PDte generated by creating a transepithelial bath-to-lumen NaCl concentration gradient, no Ca2+ and Mg2+ reabsorption was noted; instead significant and sustained Ca2+ and Mg2+ net secretion occurred. When a lumen-positive PDte was generated in the absence of apical furosemide, but in the presence of a transepithelial bath-to-lumen NaCl concentration gradient, a huge Ca2+ net secretion and a lesser Mg2+ net secretion, not modified by ADH, were observed. Replacement of Na+ by K+ in the lumen perfusate induced, in the absence of PDte changes, important but reversible net secretions of Ca2+ and Mg2+. In conclusion, our results indicate that the passive permeability of the mouse mTAL to divalent cations is very low and not influenced by ADH. This nephron segment can secrete Ca2+ and Mg2+ into the luminal fluid under conditions which elicit large lumen-positive transepithelial potential differences. Given the impermeability of this epithelium to Ca2+ and Mg2+, the secretory processes would appear to be of cellular origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900106
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  • 3
    Electronic Resource
    Electronic Resource
    Dependence of water movement on sodium transport in kidney proximal tubule: A microperfusion study substituting lithium for sodium (1981)
    Springer
    The journal of membrane biology 62 (1981), S. 105-111 
    Details
    ISSN: 1432-1424
    Keywords: Water fluxes ; Na fluxes ; proximal tubule microperfusion ; Li substitution ; rat kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The relationship between water and sodium movements through the mammalian proximal convoluted tubule was investigated by substituting lithium for sodium. Proximal convoluted rat Kidney tubules were perfusedin vivo with a Ringer solution containing 107 meq/liter lithium and 42 meq/liter sodium. Several micropunctures were made along the same nephron, and [3H] inulin, [14C] glucose,22Na, osmolality, Na, Mg and Cl were determined on each sample. Measurements of22Na showed that sodium and lithium diffusion rates were practically identical throughout the entire epithelium. A one- for-one exchange of sodium for lithium induced a negative trans-epithelial net flux of Na from plasma to lumen. However, despite this negative flux, a positive net water movement was measured from lumen to plasma. This movement was proportional both to glucose reabsorption and to the rise in the chloride concentration, two mechanisms known to be dependent on the trans-cellular movement of sodium. It was therefore concluded that the net water flux was a function of the unidirectional transcellular net flux of Na. Rabbit proximal convoluted tubules were perfusedin vitro with a solution containing 75 meq/liter Li and 75 meq/liter Na on both the luminal and peritubular sides. Under these conditions, the water reabsorption rate dropped to half its control value. Water movement was therefore a function of the external sodium concentration, which in turn probably regulates the intracellular Na concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870204
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  • 4
    Electronic Resource
    Electronic Resource
    Kidney (1973)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 35 (1973), S. 17-54 
    Details
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ph.35.030173.000313
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  • 5
    Electronic Resource
    Electronic Resource
    Hormonal Regulation of Chloride Transport in the Proximal and Distal Nephron (1988)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 50 (1988), S. 123-140 
    Details
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ph.50.030188.001011
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Phosphate reabsorption in rat nephron terminal segments (1977)
    Springer
    Pflügers Archiv 371 (1977), S. 39-44 
    Details
    ISSN: 1432-2013
    Keywords: Renal phosphate reabsorption ; Intrarenal heterogeneity ; Strain differences ; Terminal nephron ; Microinjection techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were carried out on female Wistar rats (180–220 g) undergoing mild salt diuresis (NaCl 2%, 0.100 ml·min−1).3H-Inulin and32P sodium phosphate were microinjected as tracer doses into early distal tubules of Saclay, Bordeaux (Evic Ceba) and Munich strains. In the first two strains, urinary recoveries of32P were significantly lower than those of3H-In. Unidirectional fluxes of P reabsorption (UFR) as per cent of the free flow distal load were, respectively, 17.0±2.2,n=21 and 11.4±1.3,n=19. In the Munich rats, UFR was 1.17±0.64,n=21, a value not significantly different from zero. Moreover, in Munich rats, the fractional phosphate reabsorption measured by clearance studies was compared to the UFR measured 1. for the whole nephron population (by injecting32P and3H-In into the renal arteries and analysing their subsequent urinary excretion) and 2. for the superficial nephron population (by tracer micro-injections into superficial glomeruli). All P urinary flow rates were identical for the 3 series of Munich rat experiments. P fractional reabsorption was 63.6±2.4%, a value in agreement with the UFR for the whole kidney: 68.8±2.4%, but not with the UFR for the superficial nephrons: 44.3±3.7%. It is concluded 1. differences in P distal reabsorption reported by other authors may be due to strain differences; 2. there is a tubular segment, inaccessible to micro-injection, which reabsorbs a large load of the filtered phosphate; 3. as recently suggested (P. Poujeol et al.: Pflügers Arch.365, 203, 1976) this segment could be formed by the arcades connecting deep nephron distal tubules to cortical collecting ducts, but a proximal reabsorption greater for the deep than superficial nephrons cannot be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580770
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  • 8
    Electronic Resource
    Electronic Resource
    Hormonal stimulation of Ca2+ and Mg2+ transport in the cortical thick ascending limb of Henle's loop of the mouse: evidence for a change in the paracellular pathway permeability (1993)
    Springer
    Pflügers Archiv 423 (1993), S. 387-396 
    Details
    ISSN: 1432-2013
    Keywords: Ca2+ transport ; Mg2+ transport ; Electron microprobe analysis ; Cortical thick ascending limb ; Furosemide ; Parathyroid hormone ; Paracellular shunt pathway permeability ; Tight junctions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent studies from our laboratory have shown that in the cortical thick ascending limb of Henle's loop of the mouse (cTAL) Ca2+ and Mg2+ are reabsorbed passively, via the paracellular shunt pathway. In the present study, cellular mechanisms responsible for the hormone-stimulated Ca2+ and Mg2+ transport were investigated. Transepithelial voltages (PDte) and transepithelial ion net fluxes (J Na, J Cl, J K, J Ca, J Mg) were measured in isolated perfused mouse cTAL segments. Whether parathyroid hormone (PTH) is able to stimulate Ca2+ and Mg2+ reabsorption when active NaCl reabsorption, and thus PDte, is abolished by luminal furosemide was first tested. With symmetrical lumen and bath Ringer's solutions, no Ca2+ and Mg2+ net transport was detectable, either in the absence or in the presence of PTH. In the presence of luminal furosemide and a chemically imposed lumen-to-bath directed NaCl gradient, which generates a lumen-negative PDte, PTH slightly but significantly increased Ca2+ and Mg2+ net secretion. In the presence of luminal furosemide and a chemically imposed bath-to-lumen-directed NaCl gradient, which generates a lumen-positive PDte, PTH slightly but significantly increased Ca2+ and Mg2+ net reabsorption. In view of the observed small effect of PTH on passive Ca2+ and Mg2+ movement, a possible interference of furosemide with the hormonal response was considered. To investigate this possibility, Ca2+ and Mg2+ transport was first stimulated with PTH in tubules under control conditions. Then active NaCl reabsorption was abolished by furosemide and the effect of PTH on J Ca and J Mg measured. In the absence of PDte and under symmetrical conditions, no Ca2+ and Mg2+ transport was detectable, either in the presence or absence of PTH. In the presence of a bath-to-lumen-directed NaCl gradient, Ca2+ and Mg2+ reabsorption was significantly higher in the presence than in the absence of PTH. Finally, when active NaCl transport was not inhibited by furosemide, but reduced by a bath-to-lumen-directed NaCl gradient, PTH strongly increased J Ca and J Mg, whereas only a small increase in PDte was noted. In conclusion, these data suggest that PTH exerts a dual action on Ca2+ and Mg2+ transport in the mouse cTAL by increasing the transepithelial driving force for Ca2+ and Mg2+ reabsorption through hormone-mediated PDte alterations and by modifying the passive permeability for Ca2+ and Mg2+ of the epithelium, very probably at the level of the paracellular shunt pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374932
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  • 9
    Electronic Resource
    Electronic Resource
    Cellular adaptation of the mouse cortical thick ascending limb of Henle's loop (CTAL) to dietary magnesium restriction: enhanced transepithelial Mg2+ and Ca2+ transport (2000)
    Springer
    Pflügers Archiv 439 (2000), S. 765-771 
    Details
    ISSN: 1432-2013
    Keywords: Cortical thick ascending limb Low-Mg2+ diet Mg2+ transport Microperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Mice aged 4 or 8 weeks were fed with a low-Mg2+ diet for 1, 2, 3 or 4 days. After 1 day of diet, the urinary excretion of Mg2+ and Ca2+ was strongly reduced in both animal groups (4 and 8 weeks), accompanied by a significant fall in plasma Mg2+ concentration and an increase in urinary volume. This profile persisted after 2, 3 or 4 days of dietary Mg2+ restriction. After 1 day of diet, transepithelial ion net fluxes of Na+, Cl–, Ca2+ and Mg2+ (J Na, J Cl, J Ca, J Mg) measured in vitro from isolated perfused cortical thick ascending limbs (CTALs) of these animals remained unchanged. After 2 days of diet, measurements of J Ca and J Mg in isolated perfused CTALs showed that transepithelial Mg2+ and Ca2+ reabsorption were enhanced in CTALs from Mg2+-depleted, 8-week-old animals, whereas transepithelial Mg2+ and Ca2+ transport were not altered in 4-week-old mice. J Na and J Cl and the transepithelial potential (PDte) were not modified in CTALs from either animal group. Our results suggest that a low-Mg2+ diet leads to urinary retention of Mg2+ and Ca2+ which is most likely due to increased Mg2+ and Ca2+ transport in the CTAL. Furthermore, in response to dietary Mg2+ restriction, the reabsorption of divalent cations in the CTAL of adult, but not of young, mice undergoes cellular adaptation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004249900197
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  • 10
    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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