Haemodynamic changes in ACTH-incuded hypertension in sheep

1. ACTH (20 microgram/kg per day) produced an elevation in blood pressure associated with an increase in cardiac output in conscious sheep, due in the first 72 h to a rise in heart rate. Stroke volume did not rise until the fourth day of ACTH treatment. 2. Calculated total peripheral resistance did not change. 3. Intreavenous administration of acebutolol prior to and during ACTH administration did not modify the rise in blood pressure, but this was associated with a rise in total peripheral resistance. 4. These studies show that while ACTH-induced hypertension is usually associated with increased cardiac output, rather than total peripheral resistance it still occurs, but is associated with a rise in total peripheral resistance if the rise in cardiac output is prevented by beta-adrenoreceptor blockade.