Influence of sodium conductances on platelet activation.
The effects of extracellular Na+ and tetrodotoxin on resting membrane potential, cytosolic free Ca2+ levels and aggregation of human platelets have been studied. Neither the decrease in extracellular Na+-concentration (from 140 mmol/l to 0 mmol/l) nor the addition of tetrodotoxin (10(-7) to 10(-5) mol/l) modified the platelet membrane potential. Zero extracellular Na+ concentration or the presence of tetrodotoxin in the medium inhibited platelet aggregation; however, K+-depolarized platelets showed an unchanged aggregation induced by ADP or thrombin in media with zero or low extracellular Na+ concentrations or in the presence of tetrodotoxin. Moreover, zero extracellular Na+ concentration or tetrodotoxin inhibited calcium mobilization in platelets during activation induced by thrombin. Hence, voltage-dependent activation linked to Na+ influx appears to be necessary for ADP- and thrombin-induced platelet aggregation under control conditions. Mechanisms for the role of Na+ conductances in platelet function are discussed.
Palés
J
J
Laboratori de Neurofisiologia i Biomembranes, Facultat de Medicina, Universitat de Barcelona, Spain.
Palacios-Araus
L
L
López
A
A
Gual
A
A
D000244:Adenosine Diphosphate / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000097:blood; D003600:Cytosol / Q000378:metabolism; D004553:Electric Conductivity; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
D013779:Tetrodotoxin; D000244:Adenosine Diphosphate; D012964:Sodium; D013917:Thrombin; D011188:Potassium; D002118:Calcium