PLASMA SULFOCONJUGATED DOPAMINE LEVELS ARE NORMAL IN PATIENTS WITH AUTONOMIC FAILURE

Plasma levels of norepinephrine (NE), dihydroxyphenylglycol (DHPG), di hydroxyphenylalanine (DOPA), dopamine (DA), and dihydroxyphenylacetic acid (DOPAC)-all of which are free catechols-and sulfoconjugated DA (D ASO(4)) were determined in 14 normal subjects and 18 patients with neu rogenic orthostatic hypotension caused by either multiple system atrop hy (MSA) (n = 11) or pure autonomic failure (n = 7). Ail free catechol s were normal in patients with MSA, whereas NE, DHPG, DA, and DOPAC le vels were significantly lower in patients with pure autonomic failure. The levels of DA-SO,, however, did not statistically differ among the three groups. The different plasma levels of free catechols in MSA an d pure autonomic failure are consistent with the view that peripheral sympathetic neurons are relatively preserved in MSA, whereas they are severely affected in pure autonomic failure. Because DASO, does not ap pear to be affected in pure autonomic failure, it appears likely that this metabolite is derived mainly from non-neural sources, such as the gastrointestinal tract, rather than from the sympathoadrenomedullary system.