1. Administration of adrenocorticotropic hormone (ACTH) to sheep produced increases in mean arterial pressure within 24 h associated with an increase in cardiac output and cardiac rate. Both cardiac output and blood pressure remained elevated over the 5 days of ACTH treatment.
2. Administration of ACTH during β-adrenoreceptor blockade resulted in an increase in blood pressure without changes in cardiac output at 24 h.
3. Administration of a combined steroid infusion over 5 days produced increases in cardiac output identical with the effects of ACTH but with a substantially smaller effect on blood pressure.
4. These data suggest that the observed changes in cardiac output produced by ACTH treatment may be associated with high blood concentrations of adrenocortical steroids rather than being necessary for the development of the hypertension.