CORONARY VASCULAR EFFECTS OF ENDOTHELIN-1 DURING ARTERIAL-HYPOTENSION

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 cont rol conditions and during arterial hypotension. Hypotension, induced b y mechanical constriction of the inferior vena cava, reduced mean syst emic arterial pressure from 92 +/- 4 to 59 +/- 4 mm Hg (p < 0.002), LC CA flow from 26 +/- 4 to 17 +/- 3 ml/min (p < 0.01), systolic LV press ure 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 r ate 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 ot her 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 ef fects of ET-1 are increased during hypotension. Therefore, heart ische mia may be aggravated in situations of arterial hypotension with incre ased plasma concentrations of ET-1.