Longitudinal Gradients for Endothelium-Dependent and -Independent Vascular Responses in the Coronary Microcirculation

• DOI: 10.1161/01.cir.92.3.518
• Publication Date: 2012-06-12T00:34:42Z
• Authors: Lih Kuo; Michael J. Davis; William M. Chilian
• Keywords: Arteriole; Coronary arteries; Coronary vessel

Background Coronary microvessels (<300 μm in diameter) have been demonstrated to be important the regulation of local resistance and flow. Recent studies also suggest that these are more responsive physiological pharmacological stimuli than conduit vessels. However, little is known regarding relative sensitivity different microvascular segments response flow (shear stress) agonists. The goal this study was test hypothesis a longitudinal gradient for shear stress– agonist-induced dilation exists coronary microcirculation. Methods Results Experiments were performed four sizes porcine subepicardial arterial microvessels: small arterioles (40±1-μm ID with resting tone); intermediate (60±1 μm); large (106±4 arteries (179±9 μm). Vessels isolated cannulated allow luminal pressure independently controlled. All vessels developed active tone (to ≈65% 75% maximum at their control pressures showed graded dilations stepwise increases stress (0 10 dynes/cm 2 ). For arterioles, magnitude increased as vessel size increased. highest produced 21±3%, 32±2%, 52±5% diameter small, intermediate, respectively. Small dilated only 22±6%. endothelium-dependent vasodilator substance P (SP) dose-dependent all threshold −16 mol/L. Arterioles maximally −9 mol/L SP. dose 80% arteries. ED 50 SP shifted right by two orders compared arterioles. Adenosine preferentially dose-response curves larger thresholds adenosine-induced −12 , −11 endothelium-independent nitroprusside identical segments. Conclusions results indicate pig circulation exhibits heterogeneity responses along network. sensitive adenosine, but shear-stress stimulation. We speculate site-specific preferential may play crucial role coordinating overall vascular function