The aortic alpha 1-adrenergic receptor in familial amyloidotic polyneuropathy.

To assess the pathophysiology of the sympathetic nervous system in familial amyloidotic polyneuropathy (FAP), we used 3H-bunazosin to identify and characterize the alpha 1-adrenergic receptor in human aortic membranes. The binding of 3H-bunazosin was rapid, readily reversible, stereospecific, and saturable. The Scatchard analysis described a single class of binding sites with a dissociation constant (KD) of 0.370 +/- 0.035 nM and a maximal binding capacity (Bmax) of 11.8 +/- 1.30 fmol/mg protein in control patients. Competition analysis demonstrated the alpha 1-adrenergic specificity of the 3H-bunazosin binding sites in human aortic membranes. The KD and Bmax of 3H-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 alpha 1-adrenergic receptors may not be the cause for denervation supersensitivity in FAP.