Original Article
European Journal of Clinical Nutrition (2006) 60, 593–597. doi:10.1038/sj.ejcn.1602355; published online 14 December 2005
The effect of L-cysteine and glutathione on inhibition of Na+, K+-ATPase activity by aspartame metabolites in human erythrocyte membrane
Guarantors: KH Schulpis and S Tsakiris.
Contributors: KHS, ST, IP, TP and ST.
K H Schulpis1, I Papassotiriou2, T Parthimos3, T Tsakiris3 and S Tsakiris3
- 1Institute of Child Health, Research Center, 'Aghia Sophia' Children's Hospital, Athens, Greece
- 2Department of Clinical Biochemistry, 'Aghia Sophia' Children's Hospital, Athens, Greece
- 3Department of Experimental Physiology, Medical School, University of Athens, Athens, Greece
Correspondence: Professor S Tsakiris, Department of Experimental Physiology, Medical School, University of Athens, PO Box 65257, GR 15401 Athens, Greece. E-mail: stsakir@cc.uoa.gr
Received 27 June 2005; Revised 31 August 2005; Accepted 14 September 2005; Published online 14 December 2005.
Abstract
Background:
Reports have implicated Aspartame (N-L-a-aspartyl-L-phenylalanine methyl ester, ASP) in neurological problems.
Aim:
To evaluate Na+, K+-ATPase activities in human erythrocyte membranes after incubation with the ASP metabolites, phenylalanine (Phe), methanol (MeOH) and aspartic acid (Asp).
Methods:
Erythrocyte membranes were obtained from 12 healthy individuals and were incubated at 37°C for 1 h with the sum or each of the ASP metabolites separately, which are commonly measured in blood after ASP ingestion. Na+, K+-ATPase and Mg2+-ATPase activities were measured spectrophotometrically.
Results:
Membrane Mg2+-ATPase activity was not altered. The sum of ASP metabolite concentrations corresponding to 34, 150 or 200 mg/kg of the sweetener ingestion resulted in an inhibition of the membrane Na+, K+-ATPase by -30, -40, -48%, respectively. MeOH concentrations of 0.14, 0.60 or 0.80 mM decreased the enzyme activity by -25, -38, -43%, respectively. Asp concentrations of 2.80, 7.60 or 10.0 mM inhibited membrane Na+, K+-ATPase by -26, -40, -46%, respectively. Phe concentrations of 0.14, 0.35 or 0.50 mM reduced the enzyme activity by -24, -44, -48%, respectively. Preincubation with L-cysteine or reduced glutathione (GSH) completely or partially restored the inhibited membrane Na+, K+-ATPase activity by high or toxic ASP metabolite concentrations.
Conclusions:
Low concentrations of ASP metabolites had no effect on Na+, K+-ATPase activity. High or abuse concentrations of ASP hydrolysis products significantly decreased the membrane enzyme activity, which was completely or partially prevented by L-cysteine or reduced GSH.
Keywords:
Aspartame, methanol, phenylalanine, aspartic acid, Na+, K+-ATPase, antioxidants
MORE ARTICLES LIKE THIS
These links to content published by NPG are automatically generated
RESEARCH
Serum paraoxonase/arylesterase activities in phenylketonuric patients on diet
European Journal of Clinical Nutrition Original Article
European Journal of Clinical Nutrition Original Article
