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Electroneutral Na+/H+exchange in brush-border membrane vesicles fromPenaeus japonicushepatopancreas
- Source :
- American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 274:R486-R493
- Publication Year :
- 1998
- Publisher :
- American Physiological Society, 1998.
-
Abstract
- An electroneutral Na+/H+exchange mechanism (dimethylamiloride inhibitable, Li+sensitive, and Ca2+insensitive) was identified in brush-border membrane vesicles (BBMV) from Kuruma prawn hepatopancreas by monitoring Na+-dependent H+fluxes with the pH-sensitive dye acridine orange and measuring22Na+uptake. Kinetic parameters measured under short-circuited conditions were the Na+concentration that yielded one-half of the maximal dissipation rate ( Fmax) of the preset transmembrane ΔpH ( KNa) = 15 ± 2 mM and Fmax= 3,626 ± 197 Δ F ⋅ min−1⋅ mg protein−1, with a Hill coefficient for Na+of ∼1. In addition, the inhibitory constant for dimethylamiloride was found to be ∼1 μM. The electroneutral nature of the antiporter was assessed in that an inside-negative transmembrane electrical potential neither affected kinetic parameters nor stimulated pH-dependent (intracellular pH > extracellular pH)22Na+uptake. In contrast, electrogenic pH-dependent22Na+uptake was observed in lobster hepatopancreatic BBMV. Substitution of chloride with gluconate resulted in increasing KNaand decreasing Δ Fmax, which suggests a possible role of chloride in the operational mechanism of the antiporter. These results indicate that a Na+/H+exchanger, resembling the electroneutral Na+/H+antiporter model, is present in hepatopancreatic BBMV from the Kuruma prawn Penaeus japonicus.
- Subjects :
- Sodium-Hydrogen Exchangers
Brush border
Physiology
Intracellular pH
Antiporter
Sodium
chemistry.chemical_element
Lithium
Amiloride
chemistry.chemical_compound
Chlorides
Penaeidae
Physiology (medical)
Electrochemistry
Extracellular
Animals
Ion transporter
Chromatography
Microvilli
Vesicle
Acridine orange
Hydrogen-Ion Concentration
Kinetics
chemistry
Calcium
Digestive System
Hydrogen
Nuclear chemistry
Subjects
Details
- ISSN :
- 15221490 and 03636119
- Volume :
- 274
- Database :
- OpenAIRE
- Journal :
- American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
- Accession number :
- edsair.doi.dedup.....6f442bea564f01604eda772383125d10