Capacitative Ca2+ entry in human platelets is resistant to nitric oxide.
Both sodium nitroprusside (SNP) and a phospholipase C inhibitor U73122, when applied to human platelets after the stimulation with thrombin (0.2 U/ml), caused dose-dependent inhibition of Ca2+ influx. The inhibition, however, was not complete for either substance and the U73122-resistant Ca2+ influx was also resistant to SNP. Two lines of evidence suggested that the SNP/U73122-resistant Ca2+ influx was due to the capacitative Ca2+ entry. First, U73122-resistant fraction of Ca2+ influx induced by thapsigargin was also resistant to SNP. Second, both U73122 and SNP failed to inhibit the Ca2+ influx induced by an acid extract from thrombin-stimulated platelets that contained the Ca2+ influx factor activity. We suggest that the capacitative Ca2+ entry in human platelets, once triggered by inositol trisphosphate-induced store-depletion, is not affected by nitric oxide.
Okamoto
Y
Y
Department of Pharmacology, Faculty of Medicine, Kyoto University, Japan.
Ninomiya
H
H
Miwa
S
S
Masaki
T
T
D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D002118:Calcium / Q000097:blood*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004351:Drug Resistance; D004533:Egtazic Acid / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009569:Nitric Oxide / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013917:Thrombin / Q000494:pharmacology; D014020:Tissue Extracts / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
D004963:Estrenes; D011760:Pyrrolidinones; D013729:Terpenes; D014020:Tissue Extracts; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D009599:Nitroprusside; D009569:Nitric Oxide; D004533:Egtazic Acid; D019284:Thapsigargin; D010738:Type C Phospholipases; D013917:Thrombin; D000252:Calcium-Transporting ATPases; D001241:Aspirin; D002118:Calcium