Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-2013
    Keywords: Nephron ; Sodium Transport ; Calcium Ions ; Antidiuretic Hormone ; Nierentubuli ; Natriumtransport ; Calciumionen ; Antidiuretisches Hormon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An proximalen Tubuli und medullären Sammelrohren von Ratten wurde der isotone Natriumtransport ΆNa iso und die Gleichgewichtskonzentrationsdifferenz Δc Na bei Nettosubstanzfluß und Nettovolumenfluß Null gemessen. Die peritubulären Capillaren waren bei diesen Messungen künstlich durchströmt, und zwar in der ersten Serie mit einer Calcium-freien Lösung bzw. einer Lösung, die 3 mÄq Ca++/l enthielt, in einer zweiten Serie mit einer Lösung, die kein ADH bzw. 5 mE/l ADH enthielt. Zugabe von ADH oder Weglassen von Calcium aus dem Perfusat hatten keinen Einfluß auf den isotonen Natriumtransport. Die Natrium-Gleichgewichtskonzentration bei Nettosubstanzfluß Null war jedoch stark erniedrigt. Die Befunde sprechen dafür, daß bei Fehlen von Calcium oder Zugabe von ADH die Permeabilität für Natriumionen erhöht ist, daß aber im Gegensatz zum Verhalten von Amphibienhäuten der aktive Natriumtransport unbeeinflußt bleibt.
    Notes: Summary Isotonic sodium transport, ΆNa iso, and the transtubular concentration difference, Δc Na, at equilibrium under conditions of zero net solvent and solute fluxes were measured in the proximal tubules and medullary collecting ducts of rats. Peritubular capillaries were simultaneously perfused, in the first group of experiments with a solution containing no Ca++ or 3 mEq/l of Ca++, and in the second group with a solution which contained either no ADH or 5 mU/l of ADH. Addition of ADH or omission of Ca++ from the capillary perfusate did not affect isotonic sodium transport. The equilibrium concentration difference of sodium, Δc Na, was, however, greatly reduced under the same conditions. The results indicate that in the absence of Ca++, or in the presence of ADH, the permeability for sodium is increased, but that in contradistinction to the behaviour of amphibian skins, active sodium transport remains unaffected.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-2013
    Keywords: Perfusion of Peritubular Capillaries ; Water Reabsorption ; Sodium Transport ; Proximal Convolution ; Collecting Duct ; peritubuläre Capillarperfusion ; Wasserresorption ; Natriumtransport ; proximales Konvolut ; Sammelrohre
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An Ratten wurden Mikropunktionsuntersuchungen am proximalen Tubulus und am Sammelrohr bei Durchblutung der peritubulären Capillaren bzw. Vasa recta sowie bei künstlicher Perfusion dieser Blutgefäße durchgeführt. In Abhängigkeit von der Höhe der interstitiellen Natriumkonzentration wurden der Nettonatriumtransport (ΆNa iso) bei gleicher Natriumkonzentration zu beiden Seiten der Tubuluswand und die Gleichgewichtskonzentrationsdifferenz (Δc Na) bei fehlendem Nettovolumen- und Nettosubstanzfluß gemessen. Bei Variation der Natriumkonzentration im Gewebe durch Perfusion der peritubulären Capillaren mit 155 bzw. 300 mÄq/l Na änderten sich weder ΆNa iso noch Δc Na für den proximalen Tubulus (ΆNa iso 8,4 bzw. 7,9·10−5 μÄq · mm−2 · sec−1; Δc Na 24 bzw. 24 mÄq/l). Veränderung der Natriumkonzentration im Blut durch Infusion hypertoner NaCl Lösung oder Peritonealdialyse mit isotoner Mannitlösung führten zu prinzipiell gleichen Ergebnissen. Bei Perfusion der Vasa recta mit Lösungen, die 145 und 300 mÄq/l Natrium entheilten, blieben ΆNa iso wie Δc Na über die Sammelrohrwand ebenfalls konstant (ΆNa iso 4,1 bzw. 4,1·10−5 μÄq · mm−2 · sec−1; Δc Na 98 bzw. 104 mÄq/l). Proximale Tubuli und Sammelrohre verhalten sich demnach bei Variation der interstitiellen Natriumkonzentration gleich. Da die Wasserresorption aus den Sammelrohren von dem durch Gegenstrommultiplikation erzeugten Natriumkonzentrationsanstieg im Markinterstitium abhängt, die Natriumresorption aus den Sammelrohren aber wie die vorliegenden Befunde zeigen von eben dieser Natriumkonzentration unabhängig ist, ist dem Warmblüterorganismus die Möglichkeit gegeben, Natrium- und Wasserresorption unabhängig voneinander zu variieren. Die Natrium- und Wasserresorption aus den Sammelrohren werden jedoch beide durch den Gehalt der Sammelrohrflüssigkeit an permeablen Nichtelektrolyten, wie z. B. Harnstoff, beeinflußt.
    Notes: Summary Micropuncture experiments were performed on proximal tubules and collecting ducts of rat kidneys with and without artificial perfusion of surrounding capillaries or vasa recta respectively. Net sodium flux (ΆNa iso) was estimated under conditions of varying but equal sodium concentrations on both sides of the tubular wall. The transtubular wall equilibrium concentration difference of sodium (Δc Na) was also measured in these nephron segments under conditions of zero volume and solute fluxes. In the proximal tubule ΆNa iso of 8.4 and 7.9×10−5 μeq × mm−2 × sec−1 at sodium concentrations of 155 and 300 meq/l in the perfusion fluid and Δc Na of 24 and 24 meq/l respectively did not vary significantly. Variations of sodium concentrations in blood produced by hypertonic saline infusion or peritoneal dialysis with mannitol resulted in essentially similar values of ΆNa iso and Δc Na. In the collecting ducts also ΆNa iso and Δc Na remained uninfluenced by induced variations in sodium concentrations of the perfusion fluid. ΆNa iso at sodium concentration of 145 and 300 meq/l in the perfusion fluid of vasa recta was 4.1 and 4.1×10−5 μeq × mm−2 × sec−1 respectively and Δc Na was 98 and 104 meq/l respectively. Water reabsorption in the collecting ducts depends on the increase of sodium concentration produced in the medulla by the countercurrent multiplier system. The results represented here indicate that, in mammals sodium reabsorption is independent from the sodium concentration of the interstitial fluid. Therefore the sodium reabsorption and the water reabsorption can be varied independently from each other. Both, sodium and water reabsorption in the collecting ducts are however dependent upon the concentrations of permeable nonelectrolytes such as urea in the collecting duct fluid.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-2013
    Keywords: Proximal Convolution ; Isotonic Reabsorption ; Bicarbonate Buffer ; Lipid Soluble Buffers ; Sodium Transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The fluid reabsorption from the proximal convolution of the rat kidney was measured with the Gertz shrinking droplet technique. Simultaneously, the peritubular capillaries were perfused with artificial solutions. In some experimental series, fluid from the shrinking droplet was withdrawn and analysed for Cl−, Na+, and osmolality so that the transtubular transport of Na+, Cl−, and HCO 3 − could be calculated. Capillary perfusate in some experiments was also withdrawn and its pH was measured. The following results were obtained: 1. With increasing concentration of HCO 3 − in the capillary perfusate, the transtubular water, sodium, chloride, and bicarbonate reabsorption increased. 2. The sulfonamide buffers sulfamerazine and glycodiazine (Redul®), which easily penetrate the tubular wall, could, in equimolar concentrations, substitute totally for the bicarbonate buffer in promoting isotonic fluid absorption. 3. Butyrate, propionate, and acetate were also effective; pyruvate, lactate, and paraaminohippurate, however, were not. 4. The effect of HCO 3 − and glycodiazine on isotonic absorption was shown to depend exclusively on the concentration of the buffer anion and not on the concentration of undissociated acid or pH. From these data it is suggested that for proximal isotonic absorption of water, sodium, and chloride, the reabsorption of buffer anions via H+ secretion and nonionic diffusion may be essential. The H+ secretion or the buffer anion absorption across the luminal cell wall may secondarily influence the active Na+ transporting mechanism located at the basal cell site either by a luminal H+−Na+ exchange mechanism or by a lyotropic effect which would increase the Na+ permeability of the luminal cell site. Thereby more Na+ would be delivered to the Na+ pumping site and the rate of Na+ pumping would be augmented.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...