The Role of Endothelin, Protein Kinase C and Free Radicals in the Mechanism of the Post-ischemic Endothelial Dysfunction in Guinea-pig Hearts

• Published in: Journal of molecular and cellular cardiology 2000-02, Vol.32 (2), p.297-310
• Main Authors: Maczewski, Michal, Beresewicz, Andrzej
• Format: Article
• Language: English
• Subjects: Acetylcholine - pharmacology; Adrenergic alpha-Antagonists - pharmacology; Alkaloids; Angiotensin; Angiotensin-Converting Enzyme Inhibitors - pharmacology; Animals; Anti-Arrhythmia Agents - pharmacology; Aspartic Acid Endopeptidases - antagonists & inhibitors; Benzophenanthridines; Bosentan; Captopril - pharmacology; Catalase - pharmacology; Coronary Vessels - physiopathology; Endothelial dysfunction; Endothelin; Endothelin-Converting Enzymes; Endothelins - physiology; Endothelium; Endothelium, Vascular - physiopathology; Enzyme Activation; Enzyme Inhibitors - pharmacology; Female; Free Radicals; Glycopeptides - pharmacology; Guinea Pigs; Heart - physiopathology; Hydroxyl radical; Ischemia/reperfusion; Isolated guinea-pig heart; Losartan - pharmacology; Male; Metalloendopeptidases; Muscle Proteins - antagonists & inhibitors; Muscle Proteins - physiology; Myocardial Ischemia - metabolism; Myocardial Ischemia - physiopathology; Myocardial Reperfusion; Myocardium - metabolism; Myocardium - pathology; Nitroprusside - pharmacology; Oxidative Stress; Phenanthridines - pharmacology; Prazosin - pharmacology; Protein kinase C; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - physiology; Reactive Oxygen Species - metabolism; Sulfonamides - pharmacology; Superoxide Dismutase - pharmacology; Tetradecanoylphorbol Acetate - pharmacology; Vasodilator Agents - pharmacology
• ISSN: 0022-2828; 1095-8584
• DOI: 10.1006/jmcc.1999.1073

Transient ischemia has been shown to impair endothelium-dependent, but not endothelium-independent, coronary vasodilation, indicating selective endothelial dysfunction. Here a hypothesis was tested that agonist mediated activation of protein kinase C (PKC) and the related overproduction of the oxidative species contribute to the mechanism of the endothelial dysfunction. Perfused guinea-pig hearts were subjected either to 30 min global ischemia/30 min reperfusion or to 30 min aerobic perfusion with a PKC activator, phorbol ester (1 n M, PMA). Coronary flow responses to a bolus of acetylcholine (ACh) and sodium nitroprusside (SNP) were used as measures of endothelium-dependent and endothelium-independent vascular function, respectively. Salicylate hydroxylation was used as the assay for the myocardial hydroxyl radical (·OH) formation. Both ischemia/reperfusion and PMA impaired the ACh response and augmented the myocardial ·OH production. The effect of ischemia/reperfusion on the ACh response: (i) was fully prevented by a PKC inhibitor, chelerythrine (2μM) and a mixed endothelin blocker, bosentan (20μM); (ii) was partially prevented by an endothelin converting-enzyme inhibitor, phosphoramidon (40μM), and superoxide dismutase (150–500 U/ml, SOD) and (iii) was affected neither by catalase (600 U/ml) nor by losartan (20μM) and captopril (250μM), nor by prazosin (10μM). SOD, but not bosentan, partially prevented the effect of PMA on the ACh response. None of the interventions studied affected the SNP response. The reperfusion-induced ·OH release was attenuated by chelerythrine and bosentan, was not affected by prazosin and was increased by SOD. These results implicate the following sequence of events in the mechanism of the post-ischemic endothelial dysfunction: ischemia/reperfusion, endothelin-induced PKC activation, increased production of superoxide and/or some of its toxic metabolite, damage to the endothelium and endothelial dysfunction. The results argue against the contribution of angiotensin II, adrenergicα1-receptors and kinins in the mechanism of the post-ischemic endothelial dysfunction in guinea-pig hearts.