Effect of angiotensin II on aldosterone secretion in canine adrenal gland in situ

To investigate the effect of angiotensin (ANG) II on aldosterone (ALDO) secretion, we measured arterial and adrenal venous plasma aldosterone concentrations in anesthetized dogs. The intraadrenal arterial infusion of ANG II (0.3 ng/kg/min) or potassium chloride (KCl) (0.6 mg/min) increased ALDO secretion. The changes in ALDO secretion in response to ANG II were tested during the concomitant arterial infusion of two graded doses of losartan (10 and 100 ng/kg/min), PD 123319 (50 and 500 ng/kg/min), nifedipine (25 and 250 ng/kg/min), or TMB-8 (2 and 20 μg/kg/min). All of these test drugs except PD123319 inhibited the ANG II-induced increase in ALDO secretion. Losartan did not affect the KCl-induced increase in ALDO secretion. These results indicate that ANG II acts on ANG II type I receptors in the adrenal gland and enhances ALDO secretion. They also suggest the involvement of both intracellular and extracellular calcium in the aldosterone response to stimulation by ANG II. Under these in vivo experimental conditions, the KCl-stimulated ALDO secretion does not appear to involve ANG II formation in the adrenal gland.