The aortic alpha1-adrenergic receptor in familial amyloidotic polyneuropathy

Summary To assess the pathophysiology of the sympathetic nervous system in familial amyloidotic polyneuropathy (FAP), we used³H-bunazosin to identify and characterize the alpha₁-adrenergic receptor in human aortic membranes. The binding of³H-bunazosin was rapid, readily reversible, stereospecific, and saturable. The Scatchard analysis described a single class of binding sites with a dissociation constant (K_D) of 0.370±0.035nM and a maximal binding capacity (Bmax) of 11.8±1.30 fmol/mg protein in control patients. Competition analysis demonstrated the alpha₁-adrenergic specificity of the³H-bunazosin binding sites in human aortic membranes. The K_D and Bmax of³H-bunazosin binding in four FAP patients was 0.274±0.052 nM and 7.79±0.15 fmol/mg protein, respectively; these values did not differ significantly from those in 14 control patients. An increase in Bmax or affinity of alpha₁-adrenergic receptors may not be the cause for denervation supersensitivity in FAP.