Characterization of Na(+)-H+ exchangers on villus cells in rabbit ileum
| Autor: | J. W. Dobbins, R. G. Knickelbein, Peter S. Aronson |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Sodium-Hydrogen Exchangers
Physiology Sodium chemistry.chemical_element Lithium Membrane Potentials Ileum Physiology (medical) medicine Animals Intestinal Mucosa Ion transporter Epithelial polarity Chromatography Lagomorpha Hepatology biology Ion exchange Microvilli urogenital system Chemistry Gastroenterology Muscle Smooth Membrane transport Hydrogen-Ion Concentration biology.organism_classification Amiloride Kinetics Jejunum Potassium Rabbits Cotransporter Carrier Proteins medicine.drug Nuclear chemistry |
| Zdroj: | The American journal of physiology. 259(5 Pt 1) |
| ISSN: | 0002-9513 |
| Popis: | The presence of Na(+)-H+ exchange activity is demonstrated on both the brush-border membrane (BBM) and the basolateral membrane (BLM) of villus cells from rabbit ileum. The possibility that the Na(+)-H+ exchange activity on the BLM represents HCO3- cotransport is excluded. The two Na(+)-H+ exchangers are then compared in terms of kinetics and substrate and inhibitor specificity. The most striking difference between the two exchangers was sensitivity to amiloride and K+. The IC50 for amiloride on the BLM was 10-fold lower than the BBM (11.2 +/- 2.1 vs. 103 +/- 20.9 microM; P less than 0.02). External K+, in concentrations as low as 10 mM, inhibited Na(+)-H+ exchange on the BBM but not on the BLM. The Na+ Km and proton Km were twice as high on the BLM exchanger (46.3 +/- 3.4 vs. 28.8 +/- 2.3 mM and 468 +/- 9 vs. 232 +/- 45 nM, respectively). Proton Vmax was similar, whereas Na+ Vmax was higher on the BLM. Inhibition by Li+ was similar on both membranes. These results indicate distinct differences between the two Na(+)-H+ exchangers. Whether these differences are due to the two different gene products or are the result of posttranslational modification of a single gene product remains to be determined. |
| Databáze: | OpenAIRE |
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