Impairment of sodium pump and Na/H exchanger in erythrocytes from non-insulin dependent diabetes mellitus patients: effect of tea catechins

Abstract

Background Tea catechins (EGCG, EGC, ECG and EC) possess many important biological properties. We evaluated the effect of tea catechins on erythrocyte membrane Na +/K +-ATPase and sodium/hydrogen exchanger (NHE) activity in normal (control) and NIDDM subjects. Methods Erythrocyte membrane Na +/K +-ATPase and NHE activity were determined in normal and non-insulin dependent diabetes mellitus (NIDDM) patients. In vitro effect of tea catechins was studied by incubating membrane/intact erythrocytes in assay medium prior to Na +/K +-ATPase/NHE activity determination. Results A 24.2% decrease in the activity of Na +/K +-ATPase ( p<0.001) and 39.37% increase in activity of NHE ( p<0.02) were observed in NIDDM subjects compared to normal. Tea catechins inhibited the activity of Na +/K +-ATPase and NHE in both normal and NIDDM erythrocytes, the effect was concentration-dependent. The inhibitory effect of EGCG and ECG at micromolar concentrations was greater compared to EGC and EC on Na +/K +-ATPase. On NHE the inhibition of tea catechins was in the order: EC>EGC>ECG>EGCG at concentrations up to 10 μmol/l. Conclusions This data may help to explain the anti-carcinogenic and cardioprotective effects of tea catechins. The effect of tea catechins on Na +/K +-ATPase and NHE may be explained due to a direct effect of these compounds on plasma membrane leading to a change in membrane fluidity.