Discrete intracellular Ca2+ pools coupled to two distinct Ca2+ influx pathways in human platelets

Ca2+ influx is an important event associated with platelet activation and r egulated by the content of intracellular Ca2+, Previous studies have sugges ted two different Ca2+ pools and two Ca2+ influx pathways exist in platelet s, In the present study, we have investigated the regulation of thrombin- a nd thapsigargin-induced Ca2+ entry into human platelets, using fluorescent indicators to monitor Ca2+ mobilization and membrane potential, It was foun d that depletion of thapsigargin-sensitive Ca2+ stores was coupled to Ca2influx through a Ca2+-selective pathway. Additional release of Ca2+ from th e thapsigargin-insensitive pool by thrombin caused the opening of a nonsele ctive cation channel. Copyright (C) 2000 National Science Council, ROC and S. Karger AG, Basel.