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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 401 (1984), S. 333-339 
    ISSN: 1432-2013
    Keywords: Low molecular weight protein ; Lysozyme ; Renal reabsorption, accumulation and degradation ; Tyrosine ; Gentamicin ; Inhibition of lysozyme degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous renal clearance studies provided quantitative data concerning renal reabsorption of proteins while the simultaneous processes of renal accumulation and degradation remain, to a great extent, insufficiently investigated. Thus, it was the aim of this study to measure renal reabsorption of egg-white lysozyme at various lysozyme concentrations and to relate the corresponding accumulation and degradation of lysozyme to the lysozyme transport rates in intact rats and isolated perfused rat kidneys. Lysozyme (with125I-lysozyme in certain experiments), was continuously infused i.v. or added to the perfusate to achieve plasma (or perfusate) concentrations of lysozyme (PLY) of approximately 50, 500 or 1000 mg·l−1 for periods of time varying between 3 and 120 or 150 min. Clearances of inulin and lysozyme or the total content of radioactivity and the trichloroacetic acid (TCA)-soluble radioactivity in the kidney tissue were determined at the end of clearance or accumulation periods. Additionally the perfusate concentration of the metabolite tyrosine was measured by high performance liquid chromatography (HPLC). The reabsorption rates of lysozyme (TLY) were concentration-dependent in both intact rats and isolated perfused rat kidney. After 25 min of lysozyme infusion, the lysozyme reabsorption rates amounted to 37, 245 and 331 μg·min−1·g−1 kidney at the above lysozyme concentrations. After the same infusion time, the accumulation rates of lysozyme were 8, 59 and 118 μg·min−1·g−1 kidney. The difference between the transport rate and accumulation rate should represent the renal degradation rate of lysozyme. The renal accumulation and degradation of lysozyme appeared to increase in a time- and concentration-dependent manner. The renal lysozyme degradation is of limited capacity as shown by measuring directly the release of the amino acid tyrosine by using HPLC. Renal degradation of lysozyme was almost totally inhibited by gentamicin in the presence of significant transport of lysozyme. The results of this study also demonstrate the ability of the rat kidney to reabsorb and accumulate large amounts of the cationic low molecular weight protein lysozyme without ultrastructural changes at plasma concentrations of lysozyme as high as 500 mg·l−1. Transmission electron microscopy indicated an increase in the number of endocytic vesicles and lysosomes at 1000 mg·l−1 plasma concentration of lysozyme after a 30 min infusion.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: d-Glucose ; Microperfusion ; Proximal Tubule ; Active Reabsorption ; Kinetic Study ; d-Glucose ; Mikroperfusion ; proximaler Tubulus ; aktive Reabsorption ; kinetische Studien
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Proximale Konvolute von Rattennieren wurden bei fehlendem Nettofluß von Natriumionen und Wasser kontinuierlich mit Lösungen perfundiert, die eined-Glucosekonzentration zwischen 0,5 und 2,0 mmol/l enthielten. Der Abfall der intraluminalend-Glucosekonzentration entlang eines Konvolutes wurde durch Absaugen der perfundierten Lösung in abnehmender Entfernung von der Perfusionsstelle verfolgt. Die pro innere Tubulusoberfläche und Zeit transportierted-Glucosemenge wird mit Abnahme der intraluminalen Glucosekonzentration kleiner. Dieses Verhalten läßt sich durch eine 2-parametrige Gleichung analog der Michealis-Menten-Kinetik beschreiben. Es errechnet sich eine maximale Transportrate,V max, von 6 · 10−10 mol · cm−2 · sec−1 und eine Halbsättigungskonzentration,K m, von 0,6 mmol/l. Die so beschriebene aktive Resorption und die von uns gefundene passive Permeabilität des proximalen Konvolutes fürd-Glucose reichen, nach angestellten Computerberechnungen zu schließen, allein nicht aus, um den Nettoglucosetransport der Gesamtniere unter Freiflußbedingungen quantitativ zu beschreiben.
    Notes: Summary The proximal convoluted tubule of rat kidney was continuously perfused with a steady state solution containing 0.5 to 2.0 mM ofd-glucose. The gradual decrease of intraluminald-glucose concentration was investigated with repeated collections of perfusate from the same tubule whereby the sequence of punctures proceeded towards the site of perfusion. The rate ofd-glucose transport per unit area decreased with decreasing intraluminald-glucose concentration. This relationship could be expressed by a two parameter system corresponding to the Michaelis-Menten equation. It was found that the local maximal transport rateV max equals 6×10−10 mol×cm−2×sec−1 andK m equals 0.6 mM. Our data on active resorption and passive permeability ofd-glucose in the proximal convolution have been subjected to computer analysis. The sum of both components ofd-glucose transport alone as measured under the condition of zero netflux of sodium chloride and water did not match the amount of net glucose transport found for the whole kidney under free-flow-conditions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 305 (1969), S. 155-166 
    ISSN: 1432-2013
    Keywords: l-Glucose ; Micropuncture and Microperfusion ; Proximal Tubule ; Active Secretion ; Kinetic Study ; l-Glucose ; Mikropunktion und Mikroperfusion ; proximaler Tubulus ; aktive Sekretion ; kinetische Studien
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Studies with the free flow micropuncture technique have shown that the ratio of TF/Pl-glucose to TF/PInulin in proximal tubular fluid, in distal tubular fluid, and in more than half of the final urine samples measured was greater than one, which suggests thatl-glucose was actively secreted. Studies with the microperfusion technique confirmed this finding and showed thatl-glucose was secreted by the proximal tubules. A maximum rate of secretion was reached at a plasma concentration of 4 mM. The tubular secretion ofl-glucose was augmented by the presence of 16.6 mMd-glucose in tubular lumen and inhibited by 10−4 M phlorizin. Kinetic analysis showed that theV max values forl-glucose secretion in the absence and in the presence ofd-glucose are 5.0×10−10 and 6.3×10−10 mol×cm−2×sec−1 respectively which were very close to the value reported for theV max ford-glucose reabsorption. However, theK m forl-glucose secretion was 3.1 mM and was reduced to 1.6 mM whend-glucose was present in the perfusion fluid. TheK m ford-glucose reabsorption has been reported to be 0.6 mM (8). The results of this investigation were interpreted as being consistant with the hypothesis thatl-glucose secretion andd-glucose reabsorption share the same carrier system.
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    ISSN: 0005-2736
    Keywords: (Rat kidney cortex) ; Amino acid effect ; Endocytosis ; Enzyme-membrane interaction ; Lysozyme ; Protein reabsorption
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0005-2736
    Keywords: (Rat kidney cortex) ; Brush-border membrane ; Endocytosis ; Lysozyme ; Membrane-protein interaction ; Protein absorption
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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