Mg 2+-ATPase activity in suckling rat brain regions in galactosaemia in vitro. l-Cysteine and glutathione effects

Abstract

Mg 2+-ATPase activity is implicated with Mg 2+ homeostasis, maintaining high brain intracellular Mg 2+ content. We determined the in vitro effects of galactose-1-phosphate (Gal-1-P), galactitol (Galtol) and galactose (Gal) {mix A = Gal-1-P(2 mM) + Galtol(2 mM) + Gal(4 mM) concentrations commonly found in patients with classical galactosaemia} or Galtol and Gal {mix B = Galtol(2 mM) + Gal(1 mM) concentrations usually measured in patients with galactokinase deficiency galactosaemia} on Mg 2+-ATPase activity in suckling rat brain frontal cortex, hippocampus or hypothalamus homogenates. Gal-1-P significantly ( p < 0.001) enhanced enzyme activity in all the brain areas measured, whereas Galtol and Gal failed to cause any effect in the same regions. Mix A remarkably ( p < 0.001) stimulated Mg 2+-ATPase in the studied areas. On the contrary, mix B had no effect. The supplementation of antioxidant l-cysteine (Cys) or reduced Glutathione (GSH) in mix A failed to reverse to normal the activated enzyme in frontal cortex and hypothalamus, while they significantly reduced Mg 2+-ATPase activation in hippocampus. Conclusions: (a) Gal-1-P enormously activated Mg 2+-ATPase in all the studied brain regions, (b) Mix A, also, excessively activated the enzyme in the same areas, (c) the production of free radicals may be implicated with the enzyme activation and (d) Cys or GSH significantly decreased the activated hippocampal Mg 2+-ATPase.