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.
BACKGROUND
Few studies have examined the effect of acute pressure overload on endothelial function in the coronary microcirculation.


RESULTS
In instrumented conscious dogs with heart rate held constant, veratrine caused a cholinergic nitric oxide (NO)-dependent increase in coronary blood flow by 23+/-3 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 (7+/-1 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 (MVO2) of LV tissue was measured in vitro in response to bradykinin with preincubation of angiotensin II for 30 minutes. Bradykinin (10(-4) mol/L)-induced reduction in MVO2 was reversed in a concentration-dependent manner by angiotensin II (38+/-1% versus 19+/-2% at 10(-8) mol/L) and restored by coincubation of AA (37+/-2%), tempol (33+/-2%), losartan (34+/-2%), or apocynin (36+/-1%). Exogenous NO-induced reduction in MVO2 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.
Kinugawa
Shintaro
S
Department of Physiology, New York Medical College, Valhalla, NY 10595, USA.
Post
Heiner
H
Kaminski
Pawel M
PM
Zhang
Xiaoping
X
Xu
Xiaobin
X
Huang
Harer
H
Recchia
Fabio A
FA
Ochoa
Manuel
M
Wolin
Michael S
MS
Kaley
Gabor
G
Hintze
Thomas H
TH
D000098:Acetophenones / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001919:Bradycardia / Q000139:chemically induced; D001920:Bradykinin / Q000494:pharmacology; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology*; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004285:Dogs; D007022:Hypotension / Q000139:chemically induced; D008026:Ligation; D019808:Losartan / Q000494:pharmacology; D017682:Myocardial Stunning / Q000209:etiology* / Q000503:physiopathology; D009569:Nitric Oxide / Q000502:physiology*; D018384:Oxidative Stress; D011312:Pressure / Q000009:adverse effects*; D012018:Reflex / Q000187:drug effects; D013113:Spin Labels; D013481:Superoxides / Q000378:metabolism; D014702:Veratrine / Q000494:pharmacology / Q000633:toxicity*
D000098:Acetophenones; D003497:Cyclic N-Oxides; D013113:Spin Labels; D013481:Superoxides; D000804:Angiotensin II; D009569:Nitric Oxide; C056165:acetovanillone; D014702:Veratrine; D019808:Losartan; D001205:Ascorbic Acid; D001920:Bradykinin; C001803:tempol