cardiovascular-agents and chelerythrine

Topics: Adenosine; Alkaloids; Animals; Benzophenanthridines; Cardiovascular Agents; Drug Therapy, Combination; Enzyme Inhibitors; Humans; Ischemic Preconditioning, Myocardial; Myocardial Ischemia; Phenanthridines; Protein Kinase C; Rabbits; Rats

1 Urocortin is a vasodilator peptide related to corticotrophin-releasing factor, which may protect endothelial function during coronary ischemia-reperfusion (I-R). The aim of this study was to study the mechanisms of this protective effect. 2 Hearts from Sprague-Dawley rats were isolated and perfused at constant flow and then exposed to 15 min global zero-flow ischemia, followed by 15 min reperfusion. The relaxation to acetylcholine (10 nM-10 microM) was recorded after pre-constriction of the coronary vasculature with U46619 (100-300 nM) in ischemic-reperfused or time-control hearts. 3 After I-R, the coronary relaxation to acetylcholine was reduced and this reduction was attenuated by treatment with urocortin (10 pM), administered before ischemia and during reperfusion. 4 This urocortin-induced improvement of the relaxation to acetylcholine was not modified by tetraethylammonium (10 mM), blocker of Ca2+ dependent-potassium channels; glibenclamide (10 microM), blocker of K(ATP) channels; N(w)-nitro-L-arginine methyl ester (L-NAME, 100 microM), blocker of nitric oxide synthesis; or meclofenamate (10 microM), blocker of cyclooxygenase, but it was abolished by chelerythrine (3 microM), blocker of protein kinase C (PKC). 5 These results suggest that urocortin may protect coronary endothelial function during I-R by activation of PKC.

Topics: Acetylcholine; Alkaloids; Animals; Benzophenanthridines; Cardiovascular Agents; Corticotropin-Releasing Hormone; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Glyburide; Heart; In Vitro Techniques; Male; Meclofenamic Acid; Myocardial Reperfusion Injury; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Perfusion; Phenanthridines; Protein Kinase C; Rats; Rats, Sprague-Dawley; Tetraethylammonium; Urocortins; Vasodilator Agents

Cardiomyocytes isolated from rabbit hearts were preconditioned in vitro by 10 min of ischemia or treatment with 100 microM adenosine. Protection was assessed as average integrated mortality following osmotic swelling and determination of viability by trypan blue exclusion over 60-180 min ischemia. Repetitive sub-maximal stimulations with 1 microM adenosine amplified the protective response. Treatment with adenosine only at the onset of prolonged ischemia afforded a dose-dependent protection. The PKC inhibitor calphostin C (500 nm) blocked preconditioning and, when added during ischemic incubation of non-preconditioned cells, significantly increased injury. The memory of adenosine-induced preconditioning decayed over a 60 min post-incubation period. Light activation of calphostin C initially added to preconditioned ischemic cells in the dark indicated that a 10 min period of PKC activity at the onset of ischemia affords full protection. The reversible PKC inhibitors chelerythrine (5 microM) or staurosporine (100 nM) added only to bracket induction of ischemia, reduced but did not abolish protection. Protection was abolished when either drug was present during induction and a subsequent 30 min post-incubation period. Staurosporine included during initiation and post-incubation but washed out in the final 5 min of post-incubation allowed significant protection to occur. It is concluded that a single adenosine receptor-stimulation induces protection as it preconditions, and PKC activity appears to be required for both induction and protection. Memory may reside in post-receptor amplification of an initial protective response.

Topics: Adenosine; Alkaloids; Animals; Benzophenanthridines; Cardiovascular Agents; Cells, Cultured; Enzyme Activation; Enzyme Inhibitors; Heart; Ischemic Preconditioning, Myocardial; Myocardial Ischemia; Myocardium; Naphthalenes; Phenanthridines; Protein Kinase C; Rabbits; Staurosporine