Lack of correlation of plasma norepinephrine and dopamine-beta-hydroxylase in hypertensive and normotensive subjects.

Abstract

THE ENZYME dopamine-0-hydroxylase (DBH), which is responsible for the formation of norephinephrine (NE) from dopamine, 1 is released along with the catecholamines from the adrenal medulla 2 and from stimulated sympathetic nerves in perfused organs. "5 The enzyme is present in plasma of man and other animals. 6 In animals, the levels of the enzyme are increased with stress 7 and decreased after chemical destruction of the sympathetic nerve endings but not after adrenalectomy.8 Thus, DBH in plasma appears to come from sympathetic nerve endings. In man, levels of DBH in plasma are reported to be increased by procedures that increase sympathetic neuronal activity, e.g., exercise, 9 "" immersion of the hand in cold water, 10 and insulin-induced hypoglycemia. 12 Basal levels of DBH vary widely between normal individuals, and the degree of elevation of the enzyme with stress is usually relatively small (10-25%), so increases in enzyme levels are not always observed after stress. 13 Furthermore, during the cold pressor test, levels of the other large protein molecules increase in parallel with DBH. U Thus, some investigators have found DBH to be a useful index of sympathetic function changes in DBH activity, Noth et al. 28 have stressed the need for the analysis of NE and DBH from the same plasma samples to determine whether DBH is an index of acute changes in sympathetic neuronal activity. In the present study, changes in plasma levels of DBH, total protein, a representative large protein molecule (prolactin), and NE are examined in normotensive, healthy subjects at rest, while standing, and after a standard exertion known to produce an increase in plasma levels of NE and pulse rate. 29 Since some studies have found DBH activity to be elevated in hypertensive patients or correlated with blood pressure 15 Methods Normotensive Caucasian volunteers (68 individuals of both sexes), without significant abnormalities on the basis of medical history and physical examination, and who ranged in age from 10 to 70 years, and 106 outpatients (age range, 16 to 78 years) with mild to moderate essential hypertension were asked not to take medication for 7 days nor tobacco, coffee, or tea for at least 3 hours prior to reporting for the test procedures. After a thorough explanation of the procedure, subjects gave written consent and they were asked to lie supine and relax in a quiet room. The needle of a "heparin lock" with a 3-way stopcock was inserted into an antecubital vein. A solution containing 30 units of sodium heparin (Upjohn) per milliliter sterile saline was used to flush the catheter and Downloaded from http://ahajournals.org by on June 7, 2019

Dopamine-beta-hydroxylase in patients with cystic fibrosis

“…The failure to establish a correlation between DBH activity and its common physiological substrate DA or its metabolic product NE also confirms previous findings that DBH activity is not a reliable index of the degree of sympathetic neuronal discharge of the catecholamines in individuals [15]. As far as DBH activity is concerned CF patients also seem to follow the pattern found in normals, in patients with hypertension and in patients with other chronic diseases [13,15,18].…”

Hemofiltration and Plasma Dopamine β-Hydroxylase Activity

“…The molecular weight of DBH is approximately 290.000 dalton. In the past, plasma DBH has been used as an indi cator of sympathetic activity in nonuremic patients [21] and in uremic patients on hemodialysis or hemofiltration [2,3,8], However, there is conflicting evidence in literature whether acute changes in DBH reflect acute changes of sympathetic activity and whether basal DBH reflects steady state sympathetic tone [21,22], Acute changes in plasma catecholamines are often paralleled [26], although not consistently so [27], by changes in plasma DBH. Such inconsistency may be due to the fact that a major portion of DBH does not enter the circulation by exocytosis of secretory granules, but by 'shedding' of membrane-bound DBH during turnover of axonal plasma membrane con stituents.…”

Variable Levels of Plasma Catecholamines and Dopamine β-Hydroxylase in Hemodialysis Patients

“…Previous studies in this laboratory [11] and by Lake et al [9] have revealed inconsistent changes in plasma DBH in patients with essential hypertension. However, in chronic pathological denervation of primary idiopathic orthostatic hypotension, plasma DBH and catecholamines were significantly depressed [13].…”

“…n = 6 [8] and 228± 10 pg/ml, n = 60 [4], but lower than reported by Lake et at. [9,10] of 304 20 pg/ml, n = 84. As with EPI, the NE levels in hemodialysis patients increase to control levels during the postdialysis period.…”