Effects of L-phenylalanine on acetylcholinesterase, (Na+,K+)-ATPase and Mg2+-ATPase activities in adult rat whole brain and frontal cortex.
The effect of different L-phenylalanine (Phe) concentrations (0.12-12.1 mM) on acetylcholinesterase (AChE), (Na+,K+)-ATPase and Mg2+-ATPase activities was investigated in homogenates of adult rat whole brain and frontal cortex at 37 degrees C. AChE, (Na+,K+)-ATPase and Mg2+-ATPase activities were determined after preincubation with Phe. AChE activity in both tissues showed a decrease up to 18% (p<0.01) with Phe. Whole brain Na+,K+-ATPase was stimulated by 30-35% (p<0.01) with high Phe concentrations, while frontal cortex Na+,K+-ATPase was stimulated by 50-55% (p<0.001). Mg2+-ATPase activity was increased only in frontal cortex with high Phe concentrations. It is suggested that: a) The inhibitory effect of Phe on brain AChE is not influenced by developmental factors, while the stimulation of Phe on brain Na+,K+-ATPase is indeed affected; b) The stimulatory effect of Phe on rat whole brain Na+,K+-ATPase is decreased with age; c) Na+,K+-ATPase is selectively more stimulated by high Phe concentrations in frontal cortex than in whole brain homogenate; d) High (toxic) Phe concentrations can affect Mg2+-ATPase activity in frontal cortex, but not in whole brain, thus modulating the amount of intracellular Mg2+.
Tsakiris
S
S
Department of Experimental Physiology, Medical School, University of Athens, Greece. stsakir@cc.uoa.gr
D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D005260:Female; D005625:Frontal Lobe / Q000201:enzymology; D007700:Kinetics; D008297:Male; D010649:Phenylalanine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010649:Phenylalanine; D000110:Acetylcholinesterase; D017301:Ca(2+) Mg(2+)-ATPase; D000254:Sodium-Potassium-Exchanging ATPase