TY - JOUR
T1 - Coronary α1-constrictor tone during renovascular hypertension
AU - Gwirtz, Patricia A.
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 1995/9/15
Y1 - 1995/9/15
N2 - Background: A coronary α1-adrenergic constrictor tone exists under conditions associated with increased sympathetic stimulation but not during resting conditions in the normal heart. During renovascular hypertension, elevated circulating angiotensin H may enhance sympathetic stimulation of the heart, even at rest. This study tested the hypothesis that an α1- adrenergic constrictor tone imposes limitations on coronary blood flow in resting dogs after development of renovascular hypertension, exacerbates coronary α-constrictor tone during exercise, and increases coronary vascular adrenergic responsiveness. Methods and Results: Left circumflex blood flow velocity (CFV), aortic pressure (AoP), and heart rate (HR) were examined in five quietly resting dogs during control conditions and after selective α1- adrenergic blockade using an intracoronary injection of 0.5 mg prazosin. In the normotensive state, AoP was 87±7 mm Hg (mean±SD), HR was 105±25 beats per minute, and CFV was 28±6 cm/s. These parameters were not affected by α1-adrenergic blockade. During submaximal exercise, removal of an α1- adrenergic constrictor resulted in a 14±4% increase in CFV (P<.05). Two weeks after development of renovascular hypertension induced by stenosis of the left renal artery, mean AoP was 114±7 mm Hg (P<.05 versus normotensive state), HR was 111±28 beats per minute, and CFV was 21±8 cm/s. In contrast to the normotensive state, α1-adrenergic blockade caused a 28±6% increase in CFV at rest (P<.05) and a 27±13% increase in CFV during exercise in the hypertensive state (P<.05 versus exercise before blockade and versus normotensive state). This resting coronary constrictor tone was associated with enhanced vasoconstrictor responsiveness to norepinephrine and phenylephrine. Conclusions: It appears that renovascular hypertension results in a significant coronary α1-adrenergic constrictor tone in the resting dog and an enhanced constrictor tone during exercise.
AB - Background: A coronary α1-adrenergic constrictor tone exists under conditions associated with increased sympathetic stimulation but not during resting conditions in the normal heart. During renovascular hypertension, elevated circulating angiotensin H may enhance sympathetic stimulation of the heart, even at rest. This study tested the hypothesis that an α1- adrenergic constrictor tone imposes limitations on coronary blood flow in resting dogs after development of renovascular hypertension, exacerbates coronary α-constrictor tone during exercise, and increases coronary vascular adrenergic responsiveness. Methods and Results: Left circumflex blood flow velocity (CFV), aortic pressure (AoP), and heart rate (HR) were examined in five quietly resting dogs during control conditions and after selective α1- adrenergic blockade using an intracoronary injection of 0.5 mg prazosin. In the normotensive state, AoP was 87±7 mm Hg (mean±SD), HR was 105±25 beats per minute, and CFV was 28±6 cm/s. These parameters were not affected by α1-adrenergic blockade. During submaximal exercise, removal of an α1- adrenergic constrictor resulted in a 14±4% increase in CFV (P<.05). Two weeks after development of renovascular hypertension induced by stenosis of the left renal artery, mean AoP was 114±7 mm Hg (P<.05 versus normotensive state), HR was 111±28 beats per minute, and CFV was 21±8 cm/s. In contrast to the normotensive state, α1-adrenergic blockade caused a 28±6% increase in CFV at rest (P<.05) and a 27±13% increase in CFV during exercise in the hypertensive state (P<.05 versus exercise before blockade and versus normotensive state). This resting coronary constrictor tone was associated with enhanced vasoconstrictor responsiveness to norepinephrine and phenylephrine. Conclusions: It appears that renovascular hypertension results in a significant coronary α1-adrenergic constrictor tone in the resting dog and an enhanced constrictor tone during exercise.
KW - autonomic agents
KW - coronary disease
KW - exercise
KW - hypertension, renal
KW - receptors, adrenergic, alpha
UR - http://www.scopus.com/inward/record.url?scp=0029148331&partnerID=8YFLogxK
U2 - 10.1161/01.CIR.92.6.1576
DO - 10.1161/01.CIR.92.6.1576
M3 - Article
C2 - 7664443
AN - SCOPUS:0029148331
VL - 92
SP - 1576
EP - 1581
JO - Circulation
JF - Circulation
SN - 0009-7322
IS - 6
ER -