Peroxynitrite induced decrease in Na+, K+-ATPase activity is restored by taurine.
OBJECTIVE
Peroxynitrite (ONOO-) is a powerful oxidant shown to damage membranes. In the present study, the effect of taurine on changes of liver plasma membrane Na+, K+-ATPase induced by ONOO- was investigated.


METHODS
Liver plasma membrane was exposed to ONOO- with or without taurine. Na+, K+-ATPase activity and lipid peroxidation as thiobarbituric acid reactive substances (TBARS) levels were measured.


RESULTS
Different concentrations of ONOO- (100, 200, 500, and 1000 micromol/L) were found to decrease liver plasma membrane Na+, K+-ATPase activity significantly. The depletion of enzyme activity was not concentration dependent. Effects of different concentrations of taurine on liver plasma membrane Na+, K+-ATPase activity were also measured. Taurine did not cause any increase in enzyme activity. When plasma membranes were treated with 200 micromol/L ONOO- with different concentrations of taurine, a restoring effect of taurine on enzyme activity was observed. TBARS levels were also measured and taurine was found to decrease the elevated values.


CONCLUSIONS
Taurine is observed to act as an antioxidant of ONOO- to decrease lipid peroxidation and thus affect liver plasma membrane Na+, K+-ATPase by restoring its activity.
Kocak-Toker
Necla
N
Department of Biochemistry, Istanbul Faculty of Medicine, Istanbul University, Capa 34093, Istanbul, Turkey. nectok@yahoo.com
Giris
Murat
M
Tülübas
Feti
F
Uysal
Müjdat
M
Aykac-Toker
Gülcin
G
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D051379:Mice; D016877:Oxidants / Q000494:pharmacology*; D030421:Peroxynitrous Acid / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013654:Taurine / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D016877:Oxidants; D030421:Peroxynitrous Acid; D013654:Taurine; D000254:Sodium-Potassium-Exchanging ATPase