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  • 1
    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
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electrophysiological analysis of bicarbonate permeation across the peritubular cell membrane of rat kidney proximal tubule (1984)
    Springer
    Pflügers Archiv 401 (1984), S. 34-42 
    Details
    ISSN: 1432-2013
    Keywords: Basolateral HCO 3 − transport ; pH ; $$p_{{\text{CO}}_{\text{2}} } $$ ; Carbonic anhydrase ; Anion substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The membrane potential response of proximal tubular cells to changing HCO 3 − concentrations was measured in micro-puncture experiments on rat kidney in vivo. No significant effect was noticed when luminal bicarbonate concentration was changed. Changing peritubular HCO 3 − by substitution with Cl− resulted in conspicuous membrane potential transients, which reached peak values after 100–200 ms and decayed towards near control with time constants of ∼2s. The polarity of the potential changes and the dependence of the initial potential deflections on the logarithm of HCO 3 − concentration suggest a high conductance of the peritubular cell membrane for HCO 3 − buffer, but not for Cl−, SO 4 2− , or isethionate. At constant pH $$t_{{\text{HCO}}_{\text{3}}^ - } $$ was estimated to amount to ∼0.68. At constant $$p_{{\text{CO}}_{\text{2}} } $$ , $$t_{{\text{HCO}}_{\text{3}}^ - } $$ was even greater because of an additional effect of OH− or respectively H+ gradients across the cell membrane. The secondary repolarization may be explained by passive net movements of K+ and HCO 3 − across the peritubular cell membrane, which result in a readjustment of intracellular HCO 3 − to the altered peritubular HCO 3 − concentration. Application of carbonic anhydrase inhibitors in the tubular lumen reduced the initial potential response by one half and doubled the repolarization time constant. The same effect occurred instantaneously when the inhibitor was applied—together with the HCO 3 − concentration step—in the peritubular perfusate. This observation demonstrates that membrane bound carbonic anhydrase is somehow involved in passive rheogenic bicarbonate transfer across the peritubular cell membrane, and suggests that HCO 3 − permeation might occur in form of CO2 and OH− (or H+ in opposite direction).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581530
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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