Cardiovascular actions of human endothelin in conscious sheep

1. Synthetic human endothelin was injected intravenously over the range 1.5-50 micrograms to examine its cardiovascular actions in conscious sheep. 2. Mean arterial pressure increased by 9-21 mmHg within 30-120 s over the range 5-50 micrograms endothelin. The increase in blood pressure was associated with increased calculated total peripheral resistance and a fall in cardiac output and heart rate. Stroke volume was increased. 3. Injection of endothelin into ganglion blocked sheep produced vasoconstriction and an increased blood pressure response associated with an attenuation of the effects on cardiac output, heart rate and stroke volume. 4. This study suggests that endothelin produces potent arterial vasoconstriction and reflex mediated effects on the heart in conscious sheep.