Endothelin-1 inhibits platelet aggregation in vivo: a study with 111indium-labelled platelets.
1. A non-invasive technique for the scintigraphic determination of 111indium-labelled platelet aggregation stimulated with submaximal doses of adenosine diphosphate (ADP, 56 micrograms kg-1 i.v.), collagen (100 micrograms kg-1 i.v.), platelet-activating factor (PAF, 0.1 microgram kg-1 i.v.) or thrombin (18 iu kg-1 i.v.) was used to investigate the platelet-inhibitory effects of endothelin 1 (ET-1) in anaesthetized rabbits in vivo. 2. ET-1 (1 nmol kg-1 i.v.) inhibited ADP-stimulated platelet aggregation in vivo; a maximum inhibition of 78% of the control value was reached at 3 min, with 45% inhibition at 15 min, and a return to control values at 30 min after injection of the peptide. 3. ET-1 (1 nmol kg-1 i.v.) inhibited in vivo platelet aggregation in response to collagen or PAF by 86% and 52%, respectively, but had no effect on thrombin-induced platelet aggregation. 4. Indomethacin (5 mg kg-1 i.v.) abolished the ET-1-induced inhibition of ADP-stimulated platelet aggregation and significantly potentiated and prolonged the pressor response brought about by ET-1. 5. In conclusion, the data demonstrate that ET-1 potently inhibits platelet aggregation in the anaesthetized rabbit in vivo by releasing a hypotensive and anti-aggregatory cyclo-oxygenase product, presumably prostacyclin, into the circulation.
William Harvey Research Institute, St Bartholomew's Hospital Medical College, London.
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Thiemermann
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D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects; D003094:Collagen / Q000494:pharmacology; D016232:Endothelins; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D066298:In Vitro Techniques; D007205:Indium Radioisotopes; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010455:Peptides / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors; D011817:Rabbits
D016232:Endothelins; D007205:Indium Radioisotopes; D010455:Peptides; D010975:Platelet Aggregation Inhibitors; D000244:Adenosine Diphosphate; D003094:Collagen