Article Text

PDF

Studies in primary hypomagnesaemia: evidence for defective carrier-mediated small intestinal transport of magnesium.
  1. P J Milla,
  2. P J Aggett,
  3. O H Wolff,
  4. J T Harries

    Abstract

    A 4 year old male with primary hypomagnesaemia was studied using balance and steady-state perfusion techniques. Magnesium balance was negative and could be accounted for by increased faecal losses, renal conservation being normal; calcium balance was normal. After oral magnesium therapy magnesium balance became positive. The perfusion studies demonstrated net loss of magnesium into the intestinal lumen when low concentrations (1 and 2 mmol/l) of magnesium were perfused in contrast with control subjects; whereas at high concentrations (10 mmol/l a net absorption of a magnitude similar to control values was observed. In the control subjects sequential perfusion of increasing concentrations of magnesium demonstrated a curvilinear relationship between rates of absorption and the lower concentrations (1, 2, and 4 mmol/l) with an apparent Km and Vmax of 4.5 mmol/l and 91 nmol/min/cm respectively. At the higher concentrations (6 and 10 mmol/l) the relationship was linear. These data suggest that two separate transport systems participate in the absorption of magnesium from the proximal small intestine; a carrier-mediated system which saturates at low intraluminal concentrations, and a simple diffusional process. The possibility of the second transport system being a carrier-mediated process with a very much higher Km cannot be excluded. In primary hypomagnaesaemia the results suggest that the primary abnormality is a defect in carrier-mediated transport of magnesium from low intraluminal concentrations of magnesium.

    Statistics from Altmetric.com

    Request permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.