The effect of galactose metabolic disorders on rat brain Na+,K+-ATPase activity.
To evaluate the effect of galactose metabolic disorders on the brain Na+,K+-ATPase in suckling rats. Separate preincubations of various concentrations (1-16 mM) of the compounds galactose-1-phosphate (Gal-1-P) and galactitol (galtol) with whole brain homogenates at 37 degrees C for 1 h resulted in a dose dependent inhibition of the enzyme whereas the pure enzyme (from porcine cerebral cortex) was stimulated. Glucose-1-phosphate (Glu-1-P) or galactose (Gal) stimulated both rat brain Na+,K+-ATPase and pure enzyme. A mixture of Gal-1-P (2 mM), galtol (2 mM) and Gal (4 mM), concentrations commonly found in untreated patients with classical galactosemia, caused a 35% (p < 0.001) rat brain enzyme inhibition. Additionally, incubation of a mixture of galtol (2 mM) and Gal (1 mM), which is usually observed in galactokinase deficient patients, resulted in a 25% (p < 0.001) brain enzyme inactivation. It is suggested that: a) The indirect inhibition of the brain Na+,K+-ATPase by Gal-1-P should be due to the presence of the epimer Gal and phosphate and that the pure enzyme direct activation by Gal-1-P and Glu-1-P to the presence of phosphate only. b) The observed brain Na+,K+-ATPase inhibitions in the presence of toxic concentrations of Gal-1-P and/or galtol could modulate the neural excitability, the metabolic energy production and the catecholaminergic and serotoninergic system.
Tsakiris
Stylianos
S
Department of Experimental Physiology, Medical School, University of Athens, Greece. stsakir@cc.uoa.gr
Marinou
Kyriakoula
K
Schulpis
Kleopatra H
KH
D000818:Animals; D000833:Animals, Suckling; D001921:Brain / Q000201:enzymology*; D002239:Carbohydrate Metabolism, Inborn Errors / Q000201:enzymology / Q000378:metabolism*; D004376:Galactitol / Q000494:pharmacology; D005690:Galactose / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D005695:Galactosephosphates / Q000494:pharmacology; D007700:Kinetics; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D005695:Galactosephosphates; D004376:Galactitol; C029973:galactose-1-phosphate; D000254:Sodium-Potassium-Exchanging ATPase; D005690:Galactose