Characterization of Mg2+ transport in brush border membrane vesicles of rabbit ileum studied with mag-fura-2

Biochim Biophys Acta. 1998 Mar 6;1370(1):51-63. doi: 10.1016/s0005-2736(97)00242-3.


Mg2+ transport in rabbit ileal brush border membrane vesicles (BBMV) was characterized by means of a modified mag-fura-2 technique. In the presence of an i>o Na+ gradient, BBMV showed a saturable Mg2+ uptake with a Km of 1.64 mmol l-1. There was no evidence of an overshoot. K+, Li+, and choline+ were as effective as Na+ in stimulating Mg2+ transport. In contrast, only a small amount of Mg2+ transport was observed in the presence either of an o>i Na+ gradient, or in an Na+ equilibrium or in the absence of Na+. Moreover, the findings that Na+ efflux was not stimulated but inhibited by outside Mg2+ and that the nonfluorescent amiloride-analogues DMA and EIPA did not affect Mg2+ transport do not favour the idea of an Mg2+/Na+ antiport system. At Cl- equilibrium, independent of the Na+ gradient, the rate of Mg2+ transport was markedly suppressed compared with the transport rate noted in the presence of an i>o Cl- gradient. The stimulating effect of inside anions could be enhanced by SCN- and decreased by SO2-4. Furthermore, nonfluorescent anion transport antagonist H2-DIDS stimulated Mg2+ transport. These findings indicate that Mg2+ transport can be modulated by inside anions. Mg2+ transport appeared to be electroneutral because it was not dependent on membrane potential. Mg2+ transport was neither stimulated by Bay K8644, a Ca2+ channel agonist, nor inhibited by verapamil, diltiazem, nifedipine and imipramine, the Ca2+ channel antagonists. It, therefore, seems unlikely that Mg2+ uses the Ca2+ transport system.

MeSH terms

  • Animals
  • Anions / metabolism
  • Anions / pharmacology
  • Antiporters / metabolism
  • Calcium Channel Agonists / pharmacology
  • Fluorescent Dyes
  • Fura-2 / analogs & derivatives*
  • Fura-2 / metabolism
  • Ileum / metabolism*
  • Ileum / ultrastructure*
  • Intestinal Mucosa / metabolism*
  • Intestinal Mucosa / ultrastructure*
  • Ion Transport / drug effects
  • Kinetics
  • Magnesium / metabolism*
  • Membrane Potentials / drug effects
  • Microvilli / metabolism
  • Rabbits
  • Sodium Chloride / metabolism


  • Anions
  • Antiporters
  • Calcium Channel Agonists
  • Fluorescent Dyes
  • sodium-magnesium antiporter
  • 2-(2-(5-carboxy)oxazole)-5-hydroxy-6-aminobenzofuran-N,N,O-triacetic acid
  • Sodium Chloride
  • Magnesium
  • Fura-2