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Coronary Microvascular Endothelial Stunning After Acute Pressure Overload in the Conscious Dog Is Caused by Oxidant Processes The Role of Angiotensin II Type 1 Receptor and NAD(P)H Oxidase

Coronary Microvascular Endothelial Stunning After Acute Pressure Overload in the Conscious Dog Is Caused by Oxidant Processes The Role of Angiotensin

Coronary Microvascular Endothelial Stunning After Acute Pressure Overload in the Conscious Dog Is Caused by Oxidant Processes The Role of Angiotensin II Type 1 Receptor and NAD(P)H Oxidase   (Citations: 9)
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Background—Few studies have examined the effect of acute pressure overload on endothelial function in the coronary microcirculation. Methods and Results—In instrumented conscious dogs with heart rate held constant, veratrine caused a cholinergic nitric oxide (NO)- dependent increase in coronary blood flow by 233 mL/min (Bezold-Jarisch reflex). Ten minutes after release of constriction of the ascending aorta to increase left ventricular (LV) systolic pressure to 214 5 mm Hg for 30 minutes, the veratrine-induced increase in coronary blood flow (71 mL/min) was reduced by 66% and remained depressed for 2 hours (ie, endothelial stunning (ES)). Nitrite production from isolated coronary microvessels during ES was not different from normal. Ascorbic acid (AA), losartan, or apocynin prevented ES. Myocardial oxygen consumption (MV ú O2) of LV tissue was measured in vitro in response to bradykinin with preincubation of angiotensin II for 30 minutes. Bradykinin (104 mol/L)-induced reduction in MV ú O2 was reversed in a concentration-dependent manner by angiotensin II (381% versus 192% at 108 mol/L) and restored by coincubation of AA (372%), tempol (332%), losartan (342%), or apocynin (361%). Exogenous NO-induced reduction in MV ú O2 was not altered by angiotensin II. Angiotensin II increased lucigenin-detectable superoxide anion in LV tissue in a manner that was inhibited by bradykinin, AA, tempol, losartan, or apocynin. Conclusions—Endothelial stunning is caused by oxidant processes inhibited by ascorbate, and the activation of NAD(P)H oxidase by increased angiotensin II plays an important role in this process. (Circulation. 2003;108:2934-2940.)
Published in 2011.
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