We examined the changes in plasma aldosterone concentration (PAC) during 3 kinds of postural stimulation tests and a metoclopramide test in 20 Japanese patients with surgically proven aldosterone-producing adenoma. In the 2-h upright test (n = 16), PAC increased (P < 0.01) in 14 of 16 patients, with a mean percent change of 135 +/-42% (+/-SD) of the supine levels without any significant change in plasma cortisol. In the furosemide-upright test (n = 17), PAC increased (P < 0.01) in 15 of 17 patients by 131 +/- 27%, with a significant increase in cortisol. However, in the furosemide upright test after dexamethasone pretreatment, which suppressed plasma cortisol during the test, PAC also increased (P < 0.01) in all 9 patients examined by 158 +/- 36%. Angiotensin-II infusion failed to increase PAC in all 4 patients examined whose PAC increased with postural stimulation tests. Injection of 10 mg metoclopramide (n = 13) induced a significant, but less marked, increase (P < 0.01) in PAC to 157 +/- 59% of basal levels, which was lower than those in previously reported series in Western countries. These results suggest that 1) there is a difference in PAC responsiveness to postural stimulation tests and to metoclopramide injection between Japanese and Western patients; and 2) the difference in the metoclopramide-induced aldosterone response implies a relative reduction of tonic dopaminergic inhibition of aldosterone secretion in our Japanese patients with aldosterone-producing adenoma.
