Further unravelling of the causes of ACTH-induced hypertension in the sheep.

1. Acute severe sodium subtraction (20-25% of total exchangeable sodium) before or during treatment with adrenocorticotrophic hormone (ACTH) does little to modify the increase in blood pressure induced by ACTH. 2. Chronic low salt diet, less than 5 mmol/day, abolishes the blood pressure increase, but the response can be restored by increasing the sodium intake to as little as 10 mmol/day. 3. 17alpha,20alpha-Dihydroxyprogesterone infused concurrently with other adrenal steroids will mimic ACTH hypertension and perhaps represents a new class of steroid capable of influencing blood pressure.