PLATELET GLUTATHIONE TRANSPORT - CHARACTERISTICS AND EVIDENCE FOR REGULATION BY INTRAPLATELET THIOL STATUS

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 K-M,K-apparent and V-max,V-apparent for GSH uptake in platelet plasma membrane vesicles were 28.0 +/- 8.4 mu M 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 mu M 1-chloro-2,4-dinitrobenzene (CDNB) increased GSH uptake by similar to 40%. The K-M,K-apparent and V-max,V-apparent for GSH uptake in intact platelets changed from 99.5 +/- 15 mu M and 42 +/- 7.5 pmol/min per 10(9) platelets, respectively, to 33.7 +/- 6.7 mu M and 21.5 +/- 6.9 pmol/min per 10(9) platelets, respectively, on reducing intraplatelet GSH with 100 mu M CDNB.