Dopamine surges in hyperadrenergic essential hypertension.

From a total of 61 referred hypertensive patients, 21 were clinically suspected of pheochromocytoma but in none was this diagnosis confirmed. Instead we found nine of the 21 patients had surges of conjugated dopamine during hyperadrenergic periods unaccounted for by rise in norepinephrine (NE) or epinephrine (E). Overall, essential hypertensive (EH) patients had in plasma (ng/ml) higher conjugated dopamine (DA) (2.3 +/- 0.2 vs 1.0 +/- 0.1, p less than 0.01), increasing with age (p less than 0.01), lower conjugated NE + E (0.6 +/- 0.1 vs 1.2 +/- 0.2, p less than 0.01), and higher free E (p less than 0.007), lower urinary free DA and total DA but higher free NE + E excretions (each p less than 0.05) than 24 control subjects. Following the DA surges, a short-lived urinary overflow of total DA occurred. The patients with DA surges were older, had a higher incidence of low conjugated NE + E (less than 0.23 ng/ml), a higher proportion of arterial free DA, and higher venous baseline conjugated plasma DA than the rest of the patients. Patients with low conjugated NE + E had in turn higher plasma DA concentrations at several regional sampling sites than patients with normal conjugated NE + E. High conjugated DA in EH probably results from pulsatile DA surges leading to a rise of baseline plasma conjugated DA. In the short run DA pulses can result in temporary alpha- and beta-adrenergic actions of huge arterial free DA concentrations prior to DA conjugation; in the long run the excessive high affinity DA conjugation may take preference to the lower affinity NE and lowest affinity E conjugation and free E increases. Both result in an acute or chronic increase of sympathetic tone.