Mechanisms of angiotensin-converting enzyme inhibitor induced thrombolysis in Wistar rats.
Our in vivo assay for thrombolysis consisted of recording the weight of platelet-rich thrombi adhering to a collagen strip that was superfused with arterial blood in extracorporal circulation of anaesthetised Wistar rats. Immediate thrombolysis occurred in response to intravenously administrated angiotensin-converting enzyme inhibitor (ACE-I) at non-hypotensive doses of 3-30 microg kg(-1) (captopril<perindopril<quinapril). The thrombolytic response lasted up to 3 h with maximum reduction of the weight of thrombus by 75%. Pretreatment with COX-1 and COX-3 inhibitors (aspirin at a low dose of 1 mg kg(-1), SC 560 and acetaminophen, 0.3-3 mg kg(-1)) slightly augmented thrombolysis by ACE-I, while COX-2 inhibitors (nimesulide and coxibs at doses <1 mg kg(-1) and aspirin at a high dose of 50 mg kg(-1)) or a kinin B2 receptor antagonist (icatibant) abolished it. NOS inhibition by L-NAME blunted and delayed thrombolysis by ACE-I. In parallel to maximum thrombolysis by quinapril (30 microg kg(-1)), plasma levels of 6-keto-PGF1alpha rose significantly from 40 +/- 7 to 554 +/- 91 pg ml(-1) (n=5, mean +/- S.D.), while basal levels of PGE2 (12 +/- 3 pg ml(-1)) and TXB2 (47 +/- 11 pg ml(-1)) remained essentially unchanged. Pretreatment with celecoxib (0.1-1.0 mg kg(-1)) abolished not only thrombolysis by quinapril but also the quinapril-induced rise in plasma 6-keto-PGF1alpha. In cultured bovine aortic endothelial cells, perindoprilate (30 microM) increased cytosolic free calcium [Ca2+]i, but this effect was by three to four orders of magnitude weaker than that of bradykinin (Bk). In aortas of Wistar rats, the transcripts of COX-2 and PGI-S were overexpressed as compared to COX-1. Thus, in blood vessels of Wistar rats, the preferable route of the PGI2 generation might lead through the COX-2 pathway. We conclude that in Wistar rats, ACE-I induces thrombolysis via accumulation of endogenous kinins over the endothelium and a subsequent activation of B2 receptors followed by the release of prostacyclin and nitric oxide. Thrombolysis by ACE-I seems to be mediated mainly through prostacyclin that is made by COX-2. It may well be that an increase in endothelial [Ca2+]i by ACE-I activates phospholipase A2, which supplies COX-2 with the substrate for making thrombolytic prostacyclin.
Pharmacology, Jagiellonian University, 16 Grzegorzecka, 31-531 Cracow, Poland. mfgrygle@cyf-kr.edu.pl
Richard J
RJ
Gryglewski
Józef
J
Swies
Wojciech
W
Uracz
Stefan
S
Chłopicki
Ewa
E
Marcinkiewicz
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000008:administration & dosage*; D000818:Animals; D001241:Aspirin / Q000494:pharmacology; D001920:Bradykinin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D011464:Epoprostenol / Q000378:metabolism*; D005343:Fibrinolytic Agents / Q000008:administration & dosage; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D051381:Rats; D015912:Thrombolytic Therapy / Q000379:methods; D013927:Thrombosis / Q000188:drug therapy / Q000378:metabolism*
D000806:Angiotensin-Converting Enzyme Inhibitors; D016861:Cyclooxygenase Inhibitors; D005343:Fibrinolytic Agents; D011464:Epoprostenol; D011451:Prostaglandin-Endoperoxide Synthases; D001241:Aspirin; D001920:Bradykinin; D002118:Calcium