Pressor inhibition of angiotensin-induced ACTH secretion

We investigated whether the pressor effects of systemically administered angiotensin II (AII) influence ACTH secretion. Adrenalectomized barbiturate-anesthetized mongrel dogs with constant low resting cortisol concentrations due to slow constant cortisol infusion received either bolus injections (2.5 μg kg−1) or 15-min i.v. infusions of a low dose (12.5 ng kg−1 min−1) of AII during which blood samples were taken for ACTH and cortisol determinations. In sequential continuous experiments in each dog, blood pressure was allowed to increase in response to AII administration or was controlled by means of concurrent i.v. injections or infusions of the hypotensive drug papaverine, or by blood withdrawal from the vena cava. When the arterial pressure rise induced by AII was substantially attenuated or prevented by papaverine administration or blood withdrawal, mean ACTH secretion rates increased 400–800% and mean ACTH concentrations increased by 280–500%. On the other hand, AII administration alone caused large i...