Sulphydryl groups involved in Na+-Li+ exchange in human erythrocytes.
Oxidative stress causes cellular injury that is thought to be due to increased cytosolic cation levels. Disturbances of a variety of mechanisms which normally maintain intracellular anion/cation homeostasis, occur during oxidative stress. Reactivity of the SH- groups essential for oubain-resistant Na(+)-Li(+) exchange by N-ethylmaleimide (NEM) and selenite was studied in human erythrocytes. In addition, the reactivity of the substances on SH- groups and Li(+) influx have been studied as a function of pH of the medium. The results show that NEM induces an irreversible inhibition of Li(+) influx. It diminishes progressively with the increasing pH of the medium. Whereas we obtain increasing intracellular Li(+) concentration with the rising selenite concentration in the medium. The maximum effect with this substance is reached at about pH 8.0. We can state that the -SH reagents (NEM and selenite) studied behave differently: NEM inhibits Li(+) influx by modifying the essential SH-groups of the membrane proteins in such a way that the exchange is reduced, whereas it maintains the Na(+) permeability almost unaltered. The slight increase in intracellular Na(+) induced by selenite suggests that the oxidative changes in the intracellular sulphydryl groups may constitute an important mechanism for the regulation of the intracellular cations.
Romano
L
L
Dipartimento di Fisiologia Generale e Farmacologia, Facoltà di Scienze MM. FF. NN., Università di Messina, Italy.
Sidoti
A
A
De Luca
G
G
Gugliotta
T
T
Romano
P
P
Scuteri
A
A
Amato
A
A
D017920:Antiporters / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D005033:Ethylmaleimide / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008094:Lithium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D018038:Sodium Selenite / Q000378:metabolism
D017920:Antiporters; C045885:sodium-lithium countertransporter; D008094:Lithium; D012964:Sodium; D018038:Sodium Selenite; D005033:Ethylmaleimide