Renin-angiotensin-aldosterone system in experimental renal hypertension in the rabbit

Hypertension was produced in 25 rabbits by constricting the right renal artery and leaving the opposite kidney intact (two-kidney hypertension). After 30 days mean arterial pressure and plasma renin activity (PRA) were significantly elevated (P less than 0.01), and arterial pressure was correlated with PRA (r = 0.551, P less than 0.01); however, not all hypertensive rabbits had elevated PRA, and in animals in which sodium balance was monitored, only rabbits in negative sodium balance had increased levels of PRA. To investigate the role of angiotensin II (A-II) in the hypertension, [1-sarcosine,8-alanine]angiotensin II was infused at 6 mug/kg per min for 30 min in anesthetized hypertensive animals (n = 25). For the group, arterial pressure fell significantly (P less than 0.01), but several animals with minimal hypertension failed to give a depressor response. The declines in arterial pressure were highly correlated with PRA (r = 0.853, P less than 0.01). Aldosterone secretion in hypertensive animals was correlated with PRA (r = 0.851, P less than 0.01). Thus, two-kidney hypertension in the rabbit persists with normal PRA, but during periods of spontaneous sodium depletion, A-II plays a role in the maintenance of the hypertension.