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Different mechanism of magnesium and calcium transport across rat duodenum

U Karbach1, A Schmitt, F H Saner

  • 1Medizinische Klinik, Klinikum Innenstadt, University of Munich, Germany.

Digestive Diseases and Sciences
|November 1, 1991
PubMed

Insights

Magnesium (Mg) is secreted across the rat duodenum, primarily via the paracellular pathway, while calcium (Ca) is absorbed. Hormones like vitamin D and dexamethasone differentially affect Mg and Ca transport.

Area of Science:

  • Physiology
  • Gastroenterology
  • Nutrient Transport

Background:

  • Understanding magnesium (Mg) and calcium (Ca) transport in the duodenum is crucial for nutrient absorption.
  • The distinct roles and mechanisms of Mg and Ca transport require detailed investigation.

Purpose of the Study:

  • To investigate the concentration and voltage dependence of Mg transport across the rat duodenum.
  • To elucidate the pathways (cellular vs. paracellular) involved in Mg and Ca transport.
  • To examine the effects of 1,25-dihydroxyvitamin D3 and dexamethasone on Mg and Ca transport.

Main Methods:

  • Ussing chamber technique for measuring mucosal (m) to serosa (s) and serosa (s) to mucosa (m) fluxes.
  • Voltage clamp experiments to assess the electrical properties of transport.
  • Varying Mg concentrations (0.5-5 mmol/liter) to determine transport kinetics.

Main Results:

  • Mg secretion was observed at all tested concentrations, predominantly through a diffusive paracellular pathway.
  • Mg transport (sm flux) was significantly higher than the diffusive component of Ca transport (ms flux).
  • 1,25-dihydroxyvitamin D3 stimulated Ca absorption, while dexamethasone affected both Mg and Ca transport, often antagonistically.

Conclusions:

  • The rat duodenum actively secretes Mg, mainly via paracellular diffusion, while absorbing Ca.
  • Mg and Ca likely utilize distinct cellular transport mechanisms.
  • Hormonal regulation plays a significant role in modulating the net absorption of these divalent cations.

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