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

To investigate the effect of angiotensin (ANG) II on aldosterone (ALDO) sec retion, we measured arterial and adrenal venous plasma aldosterone concentr ations 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 secr etion. The changes in ALDO secretion in response to ANG II were tested duri ng the concomitant arterial infusion of two graded doses of losartan (10 an d 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 mu g/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 i ndicate that ANG II acts on ANG II type 1 receptors in the adrenal gland an d enhances ALDO secretion. They also suggest the involvement of both intrac ellular and extracellular calcium in the aldosterone response to stimulatio n by ANG TI. Under these in vivo experimental conditions, the KCl-stimulate d ALDO secretion does not appear to involve ANG II formation in the adrenal gland.