Reduced Mg²⁺- ATPase Activity in the Hypoglycemic Adult Rat Brain

Abstract

The effects of different a-D-Glucose (Glu) concentrations (0 -16 mᴍ) on Na+, K+-ATPase and Mg2+-ATPase activities were investigated in homogenates of adult male rat whole brain at 37 °C. The enzyme activities were determined after 1h 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 mᴍ. The enzyme was inhibited 40%, 50% or 80% with 3, 2 or 1 mᴍ 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.

Effects of Calcium on the GABA<sub>A</sub>-Coupled CI<sup>-</sup>/HCO<sub>3</sub><sup>-</sup> -ATPase from Plasma Membrane of Rat Brain

“…In particular, it was shown that EGTA (EDTA) and Ca 2+ can modify the neuronal membrane Na + , K + -ATPase [19] [20]. At the same time, there was observed a change in the activity of both transport P-type ATPases and "total" Mg 2+ -ATPase or "basal" Mg 2+ -ATPase that are insensitive to ouabain [21] [22]. Therefore, we investigated the effect of Ca 2+ on the "basal" and Cl − , "basal" Mg 2+ -ATPase decreased to 55% and amounted to 4.4 µmol P i /h/mg protein.…”