Membrane depolarization inhibits thrombin-induced calcium influx and aggregation in human platelets.
The relationship between thrombin-evoked changes in intracellular calcium concentration [( Ca2+]i) and aggregation was examined in Indo-1-loaded human platelets. The stimulus-induced intracellular calcium release and external calcium influx, as well as platelet aggregation, were studied in the same cell preparation. A close correlation between the sustained high [Ca2+]i level, depending on calcium entry, and the aggregation response was found. Gramicidin, at a concentration high enough to induce membrane depolarization, strongly inhibited the calcium influx and aggregation, but did not influence the thrombin-induced intracellular calcium release. We conclude that calcium influx through depolarization-inhibited calcium channels is a prerequisite of thrombin-induced platelet aggregation.
National Institute of Haematology and Blood Transfusion, Budapest, Hungary.
T
T
Kovács
A
A
Tordai
I
I
Szász
B
B
Sarkadi
G
G
Gárdos
D001792:Blood Platelets / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D003593:Cytoplasm / Q000502:physiology; D004533:Egtazic Acid / Q000494:pharmacology; D006096:Gramicidin / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008564:Membrane Potentials; D010974:Platelet Aggregation; D015398:Signal Transduction; D013917:Thrombin / Q000494:pharmacology*
D006096:Gramicidin; D004533:Egtazic Acid; D013917:Thrombin; D002118:Calcium