[Value of the study of circulating adrenergic receptors in the diagnosis and surveillance after surgery of pheochromocytoma].

The purpose of the study was to investigate leukocyte beta adrenoceptors and platelet alpha 2 adrenoceptors in pheochromocytoma. The study concerned nine hypertensive patients, five men and four women (aged 42 +/- 8 years) with a pheochromocytoma demonstrated by high levels of urinary catecholamines and radiological data. Catecholamine plasma levels, assayed by HPLC were wide-ranging: 10.7 to 172.8 nM for noradrenaline and 0.7 to 3.9 nM for adrenaline. In each case the number of leukocyte beta adrenoceptors sites (measured with 125 I-cyanopindolol) significantly decreased: Bmax was 20.6 +/- 2.8 versus 48.5 +/- 1.5 fmol/mg protein in controls (p less than 0.05). In contrast, the number of platelet alpha 2 adrenoceptors sites (measured with 3H-yohimbine) was not modified: 206 +/- 22.6 versus 186.0 +/- 12.1 fmole/mg protein in controls. There was no change in affinity constant (Kd), neither for beta nor alpha2 adrenoceptors. After tumor removal, there was a significant increase in beta adrenoceptor number. We conclude that down regulation occurs in vivo for beta adrenoceptors but not for alpha2 adrenoceptors and that the decrease in leukocyte beta adrenoceptor number is an interesting and suitable index in the management of pheochromocytoma.