Plasma Renin Activity in Pheochromocytoma

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Plasma renin activity was measured in seven patients with pheochromocytoma. Increased plasma renin activity was consistently observed in five cases, in whom urinary excretion of noradrenaline was higher than that of adrenaline. In one patient, there occurred a progressive rise in plasma renin activity with a proportionate increase in urinary excretion of noradrenaline. On the other hand, plasma renin activity remained to be normal in the remaining cases, in whom adrenaline excretion was dominant as compared with noradrenaline excretion. These findings could be reproduced in nineteen dogs, when they were infused intravenously with noradrenaline, adrenaline, methoxamine and metaraminol. On the infusion of noradrenaline, plasma renin activity was significantly increased. In contrast, adrenaline infusion caused no change in plasma renin activity. However, in dogs premedicated with a beta-receptor blocking agent, plasma renin activity was significantly increased in response to adrenaline infusion. These findings suggest that increased plasma renin activity in pheochromocytoma is due to renal ischemia resulting from the vasoconstrictive action of noradrenaline secreted from the tumors.