N-ethylmaleimide inhibits Ca2+ influx induced by collagen or arachidonate on rabbit platelets.
N-Ethylmaleimide dose dependently inhibited platelet aggregation induced by collagen or arachidonate but did not inhibit the aggregation by thrombin or ionophore A23187 within the concentrations tested. [3H]Arachidonate release from membrane phospholipids of the collagen-stimulated platelets was inhibited by N-ethylmaleimide in parallel with the inhibition of aggregation, but not in response to A23187. N-Ethylmaleimide prevented 45Ca2+ influx into platelet cells from outer medium induced by collagen, and also inhibited the increase in the concentration of cytoplasmic free Ca2+, which probably results from Ca2+ influx, as monitored by quin2 fluorescence, under stimulation with arachidonate. The concentration of N-ethylmaleimide giving a complete inhibition of Ca2+ influx was consistent with that required to inhibit collagen- or arachidonate-induced aggregation. Prostaglandin metabolism from arachidonate to thromboxane A2 was not disturbed by N-ethylmaleimide, while phosphatidate formation induced by arachidonate was slightly inhibited by it at concentrations at which aggregation was completely inhibited. These data suggest that N-ethylmaleimide preferentially suppresses increase in cytoplasmic free Ca2+ which is linked to thromboxane A2-receptor occupation in collagen- or arachidonate-stimulated platelets, probably due to blockage of Ca2+ influx through Ca2+-channel protein, thereby inhibiting aggregation induced by these agonists.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000037:antagonists & inhibitors* / Q000097:blood; D001692:Biological Transport / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood*; D002462:Cell Membrane / Q000378:metabolism; D003094:Collagen / Q000037:antagonists & inhibitors*; D003593:Cytoplasm / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology*; D008563:Membrane Lipids / Q000097:blood; D010712:Phosphatidic Acids / Q000097:blood; D010743:Phospholipids / Q000097:blood; D010974:Platelet Aggregation / Q000187:drug effects*; D011817:Rabbits; D013917:Thrombin / Q000494:pharmacology
D001095:Arachidonic Acids; D008563:Membrane Lipids; D010712:Phosphatidic Acids; D010743:Phospholipids; D016718:Arachidonic Acid; D000001:Calcimycin; D003094:Collagen; D013917:Thrombin; D005033:Ethylmaleimide; D002118:Calcium