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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, RESULTS. Meshes: Acetylcholine, Adenosine, Adrenergic beta-Agonists, Animals, Calcium Channel Blockers, Cardiomyopathy, Dilated, Coronary Circulation, Dogs, Endothelium, Vascular, Endothelium-Dependent Relaxing Factors, Isoproterenol, Nicardipine, Nitric Oxide, Nitric Oxide Donors, Nitroglycerin, Vasodilation, Vasodilator Agents.
user
Are coronary blood flow responses impaired independent of NO and endothelial function in conscious dogs with dilated cardiomyopathy? Context: Dilated cardiomyopathy (DCM) is characterized by nitric oxide (NO) deficiency and endothelial dysfunction. Whether endothelium-independent vasodilation is preserved, particularly in the coronary circulation, remains controversial. We studied systemic and coronary flow responses to the endothelium-dependent agonist, acetylcholine, the cGMP-dependent NO-donor, nitroglycerin, the predominantly endothelium-independent agonist, adenosine, the beta-adrenergic cAMP-dependent agonist, isoproterenol, and the calcium channel antagonist, nicardipine, in conscious dogs with pacing-induced DCM. Systemic blood flow response was impaired to acetylcholine but preserved to other vasodilators in DCM. In contrast, coronary blood flow response was significantly ( P < .05) depressed to all agonists. (Peak coronary blood flow response, control versus DCM: acetylcholine: 221 +/- 14% versus 156 +/- 11%; nitroglycerin: 220 +/- 17% versus 138 +/- 9%; adenosine: 635 +/- 65% versus 376 +/- 56%; nicardipine: 338 +/- 59% versus 115 +/- 23%; isoproterenol: 219 +/- 18% versus 86 +/- 20%). The attenuation was independent of systemic hemodynamic differences.
assistant
In contrast to systemic responses, coronary blood flow responses in DCM are impaired dependent or independent of NO or second messenger mechanisms, implying either distal signaling defects or structural abnormalities in the coronary vasculature. Final Decision: yes