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The Journal of Thoracic and Cardiovascular Surgery, Vol 104, 357-363, Copyright © 1992 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
FW Sellke and JE Quillen
Ischemia and reperfusion alter the reactivity of large coronary arteries,
but the effect of ischemia and reperfusion on the coronary microcirculation
has been less well defined. Elevated circulating levels of vasopressin are
associated with cardiopulmonary bypass and numerous other clinical states
in which vascular ischemia and reperfusion may occur. We examined the
effects of ischemia with and without reperfusion on the responses to
vasopressin of both large coronary arteries and coronary arterial
microvessels. Studies were performed on vessels from control dogs (n = 8),
dogs undergoing 1 hour of ischemia only (n = 8), and dogs undergoing 1 hour
of ischemia followed with 1 hour of reperfusion (n = 9). Rings of proximal
obtuse marginal coronary arteries distal to the site of circumflex coronary
artery occlusion were studied in isolated organ chambers. Coronary
microvessels (110 to 220 microns in diameter) were studied in a pressurized
(20 mm Hg), no-flow state with a microvessel imaging apparatus and
electronic dimension analyzer. Microvessels were preconstricted with the
thromboxane A2 analog U46619. Responses of large vessel rings were studied
in the nonpreconstricted state and after preconstriction with prostaglandin
F2 alpha. Large vessel response to vasopressin was minimal and not altered
by ischemia with or without reperfusion. In contrast, ischemia markedly
affected the coronary microvascular response to vasopressin (10 to 1000
microU/ml). Control coronary microvessels constricted minimally to
vasopressin (4% +/- 2% of the baseline diameter), while microvessels after
either ischemia alone or ischemia followed by reperfusion constricted 22%
+/- 5% and 21% +/- 3%, respectively (p less than 0.05 versus control for
both). Hemoglobin, which inactivates the endothelium-derived relaxing
factor, augmented microvascular constrictions to vasopressin in all groups
to a similar extent. Relaxations to the endothelium-independent agent
nitroglycerin were not altered by ischemia. Constrictions of the coronary
microcirculation to vasopressin in conditions such as cardiopulmonary
bypass or myocardial ischemia, in which circulating levels of vasopressin
are increased, may predispose to persistent myocardial ischemia in the
perioperative setting.
ARTICLES
Altered effects of vasopressin on the coronary circulation after ischemia
Dana Cardiovascular Research Laboratory, Beth Israel Hospital, Boston, MA 02215.
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