Renin and aldosterone secretion in pheochromocytoma. Effect of chronic alpha-adrenergic receptor blockade

Patients suffering from pheochromocytoma characterized by an exclusive or almost exclusive excess of norepinephrine showed no (one patient) or only a moderate increase (two patients) in renin and aldosterone secretion. In those three patients with concomitant distinct hypersecretion of epinephrine, renin release (and aldosterone secretion except in one patient) was markedly enhanced. Similar results were obtained in a patient with excess norepinephrine and dopamine secretion. Renin release was markedly reduced in all patients during preoperative long-term alpha-adrenergic receptor blockade. With the exception of one patient, increased renin and aldosterone secretion was abolished. The results indicate that augmentation in renin release depends on the ratio of the different catecholamines secreted by the pheochromocytoma and their different effe-tiveness in stimulating beta-adrenergic receptors. Even in the presence of excess catecholamine secretion, there is evidence that renin secretion is predominantly mediated by beta receptors rather than by renal vascular alpha-adrenergic receptors. Normalization of catecholamine-induced enhanced renin release in patients with pheochromocytoma during chronic alpha-adrenergic receptor blockade supports the assumption that (alpha-) adrenergic blocking agents inhibit renin secretion distal to their blockade of specific adrenergic receptors. However, contrary to beta-adrenergic blockade, circadian rhythm of renin release seems to remain intact during alpha-adrenergic blockade.