Alpha 2-adrenergic receptor in familial amyloidotic polyneuropathy

alpha 2-Adrenergic receptor binding has been studied in platelet membranes from 16 patients with type 1 familial amyloidotic polyneuropathy (FAP) at various clinical stages and 15 normal subjects. Binding of the radioligand [3H]yohimbine to platelet membranes was used to examine alpha 2-adrenergic receptors. The number of alpha 2-adrenergic receptors were significantly lower in patients of the early stage than in normal subjects. Then, the numbers tended to be higher than those of normal subjects in the intermediate stage, and they were higher in the single advanced-stage patient studied. The reduction in alpha 2-adrenergic receptor numbers in platelet membranes from patients of the early stage might be explained by the down-regulation of the receptors in vascular smooth muscle, but it remains uncertain whether a high number of alpha 2-adrenergic receptors observed in the single advanced-stage patient might be explained by the up-regulation of the receptors.