Platelet glutathione transport: characteristics and evidence for regulation by intraplatelet thiol status

Abstract

The present study demonstrates the carrier-mediated uptake of intact glutathione (GSH) by human platelets. Platelet GSH uptake was characterized as being Na+ independent and saturable. The KM, apparent and Vmax, apparent for GSH uptake in platelet plasma membrane vesicles were 28.0 +/- 8.4 microM and 263.5 +/- 28.5 pmol/min per mg protein, respectively. The transport was inhibited by GSH analogs and enhanced by KCl-induced membrane depolarization. GSH transport may be regulated by the intracellular thiol status, since the depletion of intraplatelet GSH with 100 microM 1-chloro-2,4-dinitrobenzene (CDNB) increased GSH uptake by approximately 40%. The KM, apparent and Vmax, apparent for GSH uptake in intact platelets changed from 99.5 +/- 15 microM and 42 +/- 7.5 pmol/min per 10(9) platelets, respectively, to 33.7 +/- 6.7 microM and 21.5 +/- 6.9 pmol/min per 10(9) platelets, respectively, on reducing intraplatelet GSH with 100 microM CDNB.