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  • 1
    Electronic Resource
    Electronic Resource
    The role of bicarbonate and other buffers on isotonic fluid absorption in the proximal convolution of the rat kidney (1971)
    Springer
    Pflügers Archiv 330 (1971), S. 149-161 
    Details
    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 In some experimental series, fluid from the shrinking droplet was withdrawn and analysed for Cl−, Na+, and osmolality so that the transtubular transport of Na+, Cl−, and HCO 3 − could be calculated. Capillary perfusate in some experiments was also withdrawn and its pH was measured.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
    URL: http://dx.doi.org/10.1007/BF00643031
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of SH-, NH2- and COOH-site group reagents on the transport processes in the proximal convolution of the rat kidney (1973)
    Springer
    Pflügers Archiv 344 (1973), S. 51-68 
    Details
    ISSN: 1432-2013
    Keywords: Proximal Kidney Tubule ; Mercurials ; SH Reagents ; Site Group Reagents ; Transtubular Transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of site group reagents were tested on the following transport processes of the proximal convolution. Isotonic Na+ absorption, evaluated by the shrinking droplet procedure, histidine and glucose transport, evaluated by measuring the respective transtubular concentration difference at zero substance and water net flux. The test substances were applied either by continuous microperfusion of the peritubular capillaries or by luminal perfusion prior to the transport tests or by addition to the luminal test solution. The SH reagents (0.2 mM) N-ethylmaleimide,p-chloromercuribenzoate (pCMB) 3,6-bis-(acetatomercurimethyl)dioxane and Mersalyl (Salyrgane) caused 50% inhibition of the isotonic Na+ absorption in approximately 1.5 min when applied to the capillary perfusate. The same effect was reached in 2–3 min by 0.2 mMp-chloromercuriphenylsulfonate, benzamido-4-iodo-acetylstilbene-2,5-disulfonate and 2,2′-dihydroperoxy-2,2′-dibutylperoxide. However, the large molecular SH reagentspCMB-dextran T10 and benzoxanthene-3,4-dicarboxylic-N-iodoacetyloligoprolyl-2-aminoethylimid, did not inhibit the isotonic Na+ absorption. If an inhibitory effect was observed on the Na+ transport its onset was faster, when the substance was applied from the blood site than when it was given from the tubular lumen. Because SH reagents inhibit the isotonic Na transport faster when applied from the blood side, and because SH reagents with MW up to 690 are inhibitory whereas larger ones with MW over 1700 are not, it seems that they exert their inhibitory action on SH groups located a) predominantly on the blood side and b) deep within the membrane and not at the surface. Histidine- and glucose transport was inhibited only when the sodium transport was inhibited considerably. The oxygen consumption of teased kidney slices is not inhibited by 0.2 mMpCMB or Mersalyl within 10 min, but it is inhibited considerably by 1 mM of these substances in the same period of incubation time. The COOH reagents N,N′-carbonyl-diimidazole and N-ethyl-N′-(3-dimethyl-aminopropyl)carbodiimid (10 mM) and the NH2 reagents 4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid, 2 Na+ (SITS) (1 mM) as well as danslychloride (applied from the lumen at 5 mM in paraffin oil) did not inhibit the isotonic Na+ absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587441
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of luminal diameter and flow velocity on the isotonic fluid absorption and36Cl permeability of the proximal convolution of the rat kidney (1971)
    Springer
    Pflügers Archiv 324 (1971), S. 288-296 
    Details
    ISSN: 1432-2013
    Keywords: Renal Microperfusion ; Isotonic Reabsorption ; Tracer Permeability ; Glomerulo Tubular Balance ; Renale Mikroperfusion ; Isotone Resorption ; Tracerpermeabilität ; Glomerulotubuläre Balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the first experimental series proximal convolutions of the rat kidney were perfused with a modified Ringer solution and the isotonic fluid absorption was measured. In a second series the tubule was perfused with equilibrium solution which contained36Cl and the chloride permeability was determined. By the recollection method each individual tubule was perfused twice either at constant luminal diameter but different perfusion rates (10:30 or 6:16 nl/min) or at constant perfusion rates but different luminal diameters (20:30 μ). The perfusate was recollected at two different sites which were at least 500 μ distant from the infusion site. The isotonic fluid absorption as well as the36Cl permeability was unchanged when the tubule was distended from 20–30 μ. Both, however, increased about 20% when the perfusion rate was increased 3-fold. The data led to the following conclusions: 1. It is unlikely that there is a flow reactor type dependence of proximal tubular transport on flow rate. 2. The tubular distension cannot be responsible for the glomerulo-tubular balance. 3. It is more advantageous to relate permeability data of the rat nephron to tubular length. 4. In microperfusion experiments non steady sampling does not affect transepithelial fluxes per unit tubular length, provided that the pump delivery is constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592457
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  • 4
    Electronic Resource
    Electronic Resource
    Sodium dependence of the amino acid transport in the proximal convolution of the rat kidney (1974)
    Springer
    Pflügers Archiv 351 (1974), S. 49-60 
    Details
    ISSN: 1432-2013
    Keywords: Amino Acid Transport ; Sodium Cotransport ; Kidney Tubules ; Kidney Micropuncture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary With the technique of stop flow microperfusion with simultaneous capillary microperfusion the zero net flux transtubular concentration differences (Δc) of labelled amino acids which are equivalent to their active transport rates were measured. Alll-amino acids tested (phenylalanine, histidine, aminobicycloheptane-carboxylic acid, aminoisobutyric acid; lysine, ornithine, arginine; aspartic acid; proline and glycine) showed a considerable Δc, i.e. active transport rate. When, however, the ambient sodium was replaced by choline the Δc values dropped to zero. An analysis of the Na+ dependence of the ornithine transport revealed that the sodium-dependence is of the mixed type, i.e. thatK m decreased andV max increased with increasing Na+ concentration to the same extent. In contrast to other biological systems no mutual interaction between the Na+-dependentd-glucose andl-histidine transport could be observed. Incidental to these studies it was observed that the active transport rate ofd-histidine was in the range of 40% of that of thel-isomer while ford-phenylalanine it was only in the range of 10% of the active transport of thel-isomer. Furthermore it was found that thel-aspartic acid transport was already saturated at a luminall-aspartic acid concentration of 0.05 mmol/l while that ofl-phenylalanine was not saturated even at a luminal concentration of 9 mmol/l.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00603510
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  • 5
    Electronic Resource
    Electronic Resource
    Specificity and sodium dependence of the active sugar tansport in the proximal convolution of the rat kidney (1974)
    Springer
    Pflügers Archiv 351 (1974), S. 35-48 
    Details
    ISSN: 1432-2013
    Keywords: Hexose Transport ; Sodium Cotransport ; Kidney Tubules ; Sugar Specificity ; Kidney Micropuncture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary With the technique of stop flow microperfusion with simultaneous capillary perfusion, the zero net flux transtubular concentration difference (Δc) of labelled sugars was measured. The following sequence of Δc values, which are a measure for the active transtubular transport rate, were evaluated:d-glucose ≅β methyl-d-glycoside 〉α-methyl-d-glycoside 〉d-galactose 〉3-O-methyl-glucose 〉d-allose. When 10−4 M phlorrhizin was given in the luminal perfusate the Δc's dropped to zero (±8%). Δc-values in the same range i.e. indicating no active transport, were found for:l-glucose,d-mannose, 2-deoxy-d-glucose,d-fructose,d-glucosamine, 6-deoxy-d-galactose (=d-fucose),d-ribose and the reference polyalcohold-mannitol. Inhibition of thed-galactose δc was achieved by 15 mmol/l of the following sugars: α-methyl-d-glycoside ≅d-glucose ≅ 6-deoxy-d-glucose 〉3-O-methyl-d-glucose an no significant inhibition byd-xylose andd-mannose. Against Δc of α-methyl-d-glucose the following inhibitory potency was observed:d-glucose 〉6-deoxy-d-glucose 〉3-O-methyl-d-glucose ≅d-galactose 〉d-xylose and no inhibition byd-mannose. When the ambient sodium was replaced by choline, the Δc values of all actively transported sugars dropped toward zero. An analysis of the Na+ dependence of the α-methyl-d-glycoside transport revealed that the sodium dependence is of the affinity type i.e. that onlyK m increased with increasing Na+ concentration whileV max remained almost constant. From these data one can conclude: 1. The Crane specificity, i.e. that only the α-position of the OH-group on carbon atom 2 is essential, which was found for the intestinal hexose transport holds for the rat proximal kidney tubule, too. 2. The hexose transport system in the rat works only when Na+-ions are present. The sodium ions augment the affinity of the hexose transport system for the hexoses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00603509
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