Plasma renin activity, aldosterone and cortisol in relation with postural changes in dogs

Experiments were carried out in six dogs anesthetized with chloralose, fixed on a tilting table and moved from the supine to the vertical posture. In one dog this postural change was done after cutting both Hering nerves, and in another one after bilateral nephrectomy (BN), these experiments being orientative. Changing the supine to the vertical posture was followed by increase in plasma renin activity (PRA) and in aldosterone and cortisol plasma concentration (p.c.) Between PRA and aldosterone p.c., there was a slight correlation, but between aldosterone and cortisol this was evident. Therefore it may be supposed that aldosterone hypersecretion is produced by ACTH hypersecretion, a common stimulatory pathway for both hormones. This stimulatory mechanism is sustained by the orientative experiment on dogs, with BN, in which supine to vertical changed posture was followed by an important aldosterone hypersecretion despite minimal values of PRA.