Diet-induced magnesium deficiency in puppies resulted in an increased rate of glucose removal from the blood after intravenous glucose infusions. The levels of immunoassayable insulin in the plasma of these animals were comparable to those of the controls. The accelerated removal of glucose from the plasma was reversed with magnesium treatment. Incubation of intact diaphragms from magnesium-deficient rats demonstrated an increased sugar (2-DG) and amino acid (AIB) uptake from magnesiumfree buffer. Although the plasma magnesium concentration rapidly decreased in the deficient rats, a considerably longer period of time elapsed before the changes in sugar transport became apparent. Kinetic studies suggested that the enhanced permeability was due to carrier mediated transport rather than to diffusion. Tissue magnesium levels remained normal despite a significant decrease in the serum magnesium. These studies suggest that some general characteristic of membrane structure and function is affected by the extracellular concentration of magnesium.

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