Journal
EUROPEAN JOURNAL OF BIOCHEMISTRY
Volume 268, Issue 10, Pages 2867-2872Publisher
WILEY
DOI: 10.1046/j.1432-1327.2001.02170.x
Keywords
magnesium transport; intestinal physiology; brush border membrane vesicles; electrodiffusive ion transport; epithelial ion transport
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Mg2+ transport across the brush border of proximal intestinal epithelium of the teleost fish Oreochromis mossambicus was investigated, using Mg-27(2+) to trace movement of Mg2+. Mg2+ uptake in brush border membrane vesicles was stimulated by a K+ diffusion potential (inside negative). Electrodiffusive Mg2+ transport obeyed simple Michaelis-Menten kinetics and was strongly temperature dependent, indicative of a carrier mechanism. The metal ion specificity of this electrodiffusive pathway (inhibition potency order: Co > Mn = Ni > La > Ca > Gd > Ba), predicts a specific role in Mg2+ transport. Competitive inhibition by Co(III) hexammine [Co(NH3)(6)(3 +) ] suggests that this transport system interacts with the solvated Mg ion. We propose that this novel transport system allows the uptake of Mg2+ across the apical brush border membrane, and is involved in transcellular Mg2+ transport. Consequently, the prevailing potential difference across the apical membrane represents a major driving force for intestinal Mg2+ absorption.
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