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Electroneutral Na+/H+exchange in brush-border membrane vesicles fromPenaeus japonicushepatopancreas

Authors :
V. Zonno
L. Ingrosso
Sebastiano Vilella
Tiziano Verri
Carlo Storelli
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.

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