Platelet α2- and leucocyte β2-adrenoceptors in phaeochromocytoma: effect of tumour removal

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Abstract
Platelet .alpha.2- and leucocyte .beta.2-adrenoceptors (as well as noradrenaline and adrenaline plasma levels) were studied in five patients with confirmed phaeochromocytoma using tritiated yohimbine and iodated cyanopindolol, respectively, before and after tumour removal. Patients with phaeochromocytoma had a lower leucocyte iodated cyanopindolol binding than control subjects, but no change in platelet triated vohimbine binding. Plasma catecholamine levels were higher than controls. Tumour removal induced a return to normal values of leucocyte iodated cyanopindolol binding and a decrease in plasma catecholamine levels. These results underline the potential interest of leucocyte .beta.-adrenoceptor quantification in the diagnosis and the follow-up of phaeochromocytoma. Pharmacologically, they show that down-regulation occurs in vivo for leucocyte .beta.2-adrenoceptors but not for platelet .alpha.2-adrenoceptors.