Electrodiffusive magnesium transport across the intestinal brush border membrane of tilapia (Oreochromis mossambicus).
Mg2+ transport across the brush border of proximal intestinal epithelium of the teleost fish Oreochromis mossambicus was investigated, using 27Mg2+ 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.
Bijvelds
M J
MJ
Department of Radiochemistry, Interfaculty Reactor Institute, Delft University of Technology, the Netherlands.
Kolar
Z I
ZI
Flik
G
G
D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004058:Diffusion; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry* / Q000378:metabolism; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism*; D011188:Potassium; D011485:Protein Binding; D013696:Temperature; D017210:Tilapia; D013997:Time Factors
D007477:Ions; D008274:Magnesium; D011188:Potassium