Abstract
Summary: Endothelin-1 (ET-1) effects on left circumflex coronary artery (LCCA) flow, systemic arterial pressure, heart rate, and left ventricle (LV) pressure and dP/dt were recorded in five anesthetized goats under control conditions and during arterial hypotension. Hypotension, induced by mechanical constriction of the inferior vena cava, reduced mean systemic arterial pressure from 92 ± 4 to 59 ± 4 mm Hg (p < 0.002), LCCA flow from 26 ± 4 to 17 ± 3 ml/min (p < 0.01), systolic LV pressure from 108 ± 2.5 to 79 ± 2 mm Hg (p < 0.002), and peak systolic LV dP/dt from 1,500 ± 106 to 990 ± 130 mm Hg/s (p < 0.02). Heart rate did not change (p > 0.05). ET-1 (0.01–0.1 nmol) injected into LCCA reduced LCCA flow in a dose-dependent manner without affecting the other variables recorded during control periods (C) and hypotension (H). The percentage reductions of LCCA flow by ET-1 were: for 0.01 nmol, 4.5 ± 2 (C) vs. 11 ± 2 (H) (p < 0.05); for 0.03 nmol, 15 ± 2 (C) vs. 32 ± 4 (H) (p < 0.05); and for 0.1 nmol, 44 ± 5 (C) vs. 67 ± 5 (H) (p < 0.05). This indicates that the coronary vasoconstrictor effects of ET-1 are increased during hypotension. Therefore, heart ischemia may be aggravated in situations of arterial hypotension with increased plasma concentrations of ET-1.
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