Reduced Mg2+-ATPase activity in the hypoglycemic adult rat brain.

The effects of different a-D-Glucose (Glu) concentrations (0-16 mM) on Na+, K+-ATPase and Mg2+-ATPase activities were investigated in homogenates of adult male rat whole brain at 37 degrees C. The enzyme activities were determined after 1 h preincubation with Glu. Brain Na+, K+-ATPase was not affected by Glu different concentrations. On the contrary, Mg2+-ATPase activity was considerably reduced with Glu concentrations lower than 4 mM. The enzyme was inhibited 40%, 50% or 80% with 3, 2 or 1 mM of Glu, respectively. The above results suggest: a) The various concentrations of Glu have no effect on brain Na+, K+-ATPase activity. b) The inhibited brain Mg2+-ATPase in hypoglycemia produces low intracellular Mg2+, which could modulate the activity of Mg2+-dependent enzymes and the rates of protein synthesis and growth of the cell.