[Lymphocyte beta 2-adrenergic receptors in pheochromocytoma]

To assess the effect of chronic exposure to high circulating catecholamine concentrations on the beta 2-adrenergic receptors, the density and affinity of lymphocyte beta 2-adrenergic receptors were measured in 5 patients with pheochromocytoma (2 males and 3 females, with a mean age of 39 +/- 12 years). In 4 patients the studies were repeated 15 days after tumor removal. Before surgery, all patients had high plasma catecholamine concentration. The density of beta 2-adrenergic receptors was reduced, although their affinity was within the reference range. There was an inverse correlation between plasma epinephrine concentration and beta 2-adrenergic receptor density (r = -0.959, p = 0.01). After surgical resection, plasma catecholamine concentrations and receptor density became normal. The dissociation constant decreased in the four patients. In conclusion, in the presence of chronically high levels of circulating catecholamines the density of lymphocyte beta 2-adrenergic receptors is reduced. However, it becomes normal when plasma catecholamine concentration returns to the reference values, the dynamic character of this regulation being thus shown. The measurement of these receptors in the lymphocyte could be useful for the diagnosis and follow up of patients with pheochromocytoma.