title: Role of protein kinase C in the anti-aggregatory effects of endothelin-1 on human platelets.
abstract: 1. Endothelin-1 has anti-aggregatory properties, but the mechanism underlying this inhibitory action is unknown. This in vitro study investigates effects of endothelin-1 on thrombin-stimulated aggregation and intracellular free calcium concentration in human platelets and assesses the role of protein kinase C in the interactions between endothelin-1 and thrombin. Aggregation was measured turbidometrically and the intracellular free calcium concentration was determined with the fluorescent indicator fura 2-acetoxymethyl ester. 2. Endothelin-1 at concentrations from 10(-11) to 10(-6) mol/l had no effect on platelet aggregation or intracellular free calcium concentration but inhibited in a dose-dependent manner aggregation induced by 0.05 unit/ml thrombin (pD2 for inhibition by endothelin = 8.1 +/- 0.12). 3. Endothelin-1 at 10(-9) mol/l significantly decreased (P < 0.01) thrombin-stimulated aggregation from 81.4 +/- 1.5% (in the absence of endothelin-1) to 53.5 +/- 1.1% (in the presence of endothelin) and thrombin-stimulated intracellular free calcium concentration from 179 +/- 1.7 nmol/l to 140 +/- 1.8 nmol/l. 4. Preincubation of platelets with 10(-7) mol/l staurosporine (protein kinase C inhibitor), calphostin C (highly selective protein kinase C inhibitor) or 5-(N,N-hexamethylene) amiloride (highly selective Na(+)-H+ exchange blocker) significantly inhibited (P < 0.01) thrombin-stimulated platelet responses and suppressed the inhibitory effect of endothelin-1 on thrombin-induced aggregation and intracellular free calcium concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Clinical Research Institute of Montreal, University of Montreal, Canada.
authors.forename: R M
authors.initials: RM
authors.lastname: Touyz
authors.forename: E L
authors.initials: EL
authors.lastname: Schiffrin
mesh_terms: D000328:Adult; D000470:Alkaloids / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000494:pharmacology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009281:Naphthalenes; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011083:Polycyclic Compounds / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors; D019311:Staurosporine; D013917:Thrombin / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D016232:Endothelins; D009281:Naphthalenes; D010975:Platelet Aggregation Inhibitors; D011083:Polycyclic Compounds; D017923:Sodium-Hydrogen Exchangers; C057360:5-(N,N-hexamethylene)amiloride; D000584:Amiloride; D011493:Protein Kinase C; D013917:Thrombin; D019311:Staurosporine; C058819:calphostin C; D002118:Calcium