Response of human blood platelet membrane to sodium selenite

It was demonstrated that incubation of blood platelets with sodium selenite (1-100 mu M) resulted in a dose- and time-dependent loss of platelet thiol s (both glutathione and protein -SH groups). The effects of sodium selenite on platelet membrane lipid fluidity by the EPR spin-labelling method was a lso investigated. We showed there were no alterations in membrane fluidity at the deeper regions (12-DOXYL-Ste) in lipid bilayer, a slight increase (a pprox. 7%, p < 0.03) of h(+1)/h(0) for spin probe 5-DOXYL-Ste was monitored . The amount of Triton-insoluble protein fraction isolated from platelets a fter incubation (60 min) with selenite was significantly elevated (p < 0.00 6). It has been suggested that limited increase in lipid fluidity at the su rface regions in the lipid bilayer of the platelet membrane in selenite-tre ated platelets may be the result of alteration in lipid-protein interaction s caused by protein conformational changes.