Coronary effects of endothelin-1 during acute hypertension in anaesthetized goats

The coronary effects of endothelin-1 (ET-1) during acute hypertension were examined in anesthetized goats, where the left circumflex coronary artery flow was electromagnetically measured and hypertension was induced by constriction of the thoracic aorta. In six non-treated goats, aortic constriction increased arterial pressure (mean arterial pressure = 128±5mmHg) and coronary flow (by 34%) without changing coronary vascular conductance. In this case, ET-1 (0.01–0.3nmol) when injected intracoronarily, decreased coronary vascular conductance, which was similar in hypertension and in normotension. In eight N^G-nitro-L-arginine methyl ester-treated goats, aortic constriction increased arterial pressure (mean arterial pressure = 131±5mmHg) and coronary flow (by 26%) and decreased coronary vascular conductance (by 17%). In this case, ET-1 (0.01–0.3nmol) also decreased coronary vascular conductance, which was similar in N^G-nitro-L-arginine methyl ester-treated hypertension that observed in normotension. Therefore, acute hypertension attenuates the coronary vasoconstriction caused by ET-1, and this attenuation might be related to mechanisms other than changes in NO release.