Dopamine β-hydroxylation in diabetes and diabetic autonomic neuropathy

Abstract

Dopamine β-hydroxylase (DBH) has been studied in healthy subjects and diabetic patients, some of whom had autonomic neuropathy. DBH was assayed by a recently described in vivo tritium release method (10,11). Dopamine specifically labeled in the β position, [β- 3H]DA, was given intravenously, and the time course of tritiated water (THO) release into the total body water was measure as an index of DBH activity in sympathetic neurons. We simultaneously assayed [ 3H]norepinephrine metabolite excretion. The DBH activity of patients with autonomic neuropathy as a group did not differ significantly from that of diabetics without neuropathy or healthy controls. Our data do not support the suggestion (7) that a deficit in DBH activity is responsible for sympathetic neuronal dysfunction in diabetic autonomic neuropathy. This syndrome thus differs from idiopathic orthostatic hypotension in which condition there is an impairment in the ability of sympathetic neurons to hydroxylate dopamine (9).