Plasma dopamine-beta-hydroxylase activity and blood pressure variability in hypertensive man.

It has been proposed that measurements of plasma dopamine-beta-hydroxylase (DBH) may allow for assessmetn of adrenergic tone and may elucidate a possible neurogenic contribution to essential hypertension. We performed a series of measurements of DBH in fifty-seven normotensive and fifty hypertensive black and white men in order (1) to compare DBH to selected blood pressure patterns and (2) to evalutate the influence of salt intake, posture and race on plasma DBH. Plasma DBH, measured on unrestricted salt intake with subjects supine, was 42 +/- 4 Units/L in white normotensives, greater (P less than 0.05) than black normotensives (26 +/- 6 Units/L). White hypertensives had greater plasma concentrations of DBH than black (35 +/- 3 VS. 24 +/- 5, P less than 0.05). Normotensives did not differ from hypertensives. Dietary salt restriction and upright ambulation increased plasma DBH activity in hypertensives. Although DBH did not correlate directly with blood pressure, high DBH values were associated with lability of blood pressure in hypertensives but not in normotensives. There are two possible explanations for our results: (1) multiple factors influence plasma DBH activity and plasma levels reflect more than adrenergic function, or (2) essential hypertension is a multifactorial disease and excess sympathetic neuronal activity alone is not sufficient to produce sustained hypertension.