Abnormality of circulatory reflex and aldosterone response during head-up tilting in patients with primary aldosteronism.

Abnormality of the circulatory reflexes has been reported in patients with primary aldosteronism. However, changes in blood pressure, heart rate, plasma renin activity (PRA), and plasma aldosterone concentration (PAC) after head-up tilting in primary aldosteronism have not yet been reported. Seven patients with primary aldosteronism were tilted to a 65 degree head-up position which was maintained for 30 min. Systolic blood pressure decreased significantly 5 min after tilting and remained at this level during the period of tilting. Diastolic blood pressure did not change during the tilting. Heart rate increased after 5 min of tilting and this level of heart rate was maintained for 30 min. Plasma renin activity was low and did not change during tilting. However, plasma aldosterone concentration increased significantly 20 min after tilting. Plasma cortisol concentration and plasma ACTH concentration also increased significantly. These results suggest that primary aldosteronism causes abnormalities of the circulatory reflexes. The increase of endogenous ACTH may increase plasma aldosterone concentration in patients with primary aldosteronism.