Functional involvement of angiotensin AT(2) receptor in adrenal catecholamine secretion in vivo

The aim of the present study was to analyse modulations of adrenal catechol amine secretion from the adrenal gland of anesthetized dogs in response to locally administered angiotensin II (AngII) in the presence of either PD 12 3319 or CGP 42112, both of which are highly specific and selective ligands to angiotensin AT(2) receptor. Plasma concentrations of epinephrine and nor epinephrine in adrenal venous and aortic blood were quantified by a high pe rformance liquid chromatography coupled with electrochemical detection (HPL C-EC) method. Adrenal venous blood flow was measured by gravimetry. Local a dministration of AngII (0.05 mu g, 0.1 mu M) to the left adrenal gland incr eased adrenal gland catecholamine output more than 30 times that found in n onstimulated states. Administration of either PD 123319 (0.085 mu g (0.23 m u M) to 8.5 mu g (23 mu M)) or CGP 42112 (0.005 mu g (0.01 mu M) to 5 mu g (10 mu M)) did not affect the basal catecholamine output significantly. The increase in adrenal catecholamine output in response to AngII was inhibite d by similar to 80% following the largest dose of PD 123319. CGP 42112 sign ificantly attenuated the catecholamine response to AngII by similar to 70%. PD 123319 and CGP 42112 were devoid of any agonist actions with respect to catecholamine output by the adrenal gland in vivo. Furthermore, both PD 12 3319 and CGP 42112 inhibited the increase in adrenal catecholamine secretio n induced by local administration of AngII. The present study suggests that AT(2) receptors play a role in mediating catecholamine secretion by the ad renal medulla in response to AngII receptor agonist administration in vivo.