Changes in platelet alpha 2-adrenoceptors in human phaeochromocytoma.

In a 44 year-old male with a surgically proven phaeochromocytoma platelet alpha 2-adrenoceptor density, determined by 3H-yohimbine binding, was only 50% of that in an age-matched control group, and plasma catecholamines were elevated. Two weeks after removal of the tumour, platelet alpha 2-adrenoceptor density and plasma catecholamines had become normal and were not significantly different from the controls. It is concluded that endogenous catecholamines may play an important role in regulation of alpha 2-adrenoceptor density and hence tissue sensitivity to alpha-adrenergic stimulation in the human being.