Plasma Dopamin-?-hydroxylase-activity in dialysed patients

Abstract

Plasma dopamin-b-hydroxylase (DBH) was studied in 70 healthy control persons and in 37 hemodialysed patients. Basal DBH in controls corresponded to 50.0 +/- 29.3 IU. There was was no significant difference between males (53.9 +/1 33.8 IU) and females (47.4 +/- 25 IU); no correlation could be found between age and plasma DBH. In hemodialysed patients basal DBH levels were significantly (p less than 0.01) decreased (32.5 %/- 17.6 IU), suggesting lowered sympathetic activity and/or abnormalities in release, distribution space, or metabolism of DBH. During hemodialysis plasma DBH activity rose during ultrafiltration. This finding indicates a directionally appropriate sympathetic reflex response to volume depletion in dialysed patients.

Hemofiltration and Plasma Dopamine β-Hydroxylase Activity

“…[20] reported elevated levels of plasma noradrenaline and/or plasma adrenaline in hemodialyzed patients. In contrast, plasma DBH values were reported to be low [8], Plasma noradrenaline levels may not necessarily reflect the efferent nerve traffic in the peripheral sympathetic nerve system, because plasma noradrenaline is the net result of discharge of secretory granules on the one hand and local reuptake, neuronal or extraneuronal metabolism on the other hand. Some of these processes may be altered in uremia [18].…”

“…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.…”

“…[8], using tyraminc as substrate at optimal pH. The incubation mixture (final volume 1.0 ml) was chosen according to the original method: diluted plasma (50 ¡¿1 diluted with distilled water to 400 ¡¿1); 1 M sodium acetate, buffered at pH 5.0, 200 ¡¿I; 0.2 M N-ethylmaleimide, 150 (¿1; 0.2 M Na-fumarate, 50 ¡/.I; 0.02 M pargyline, 50 ¡¿1:0.2 M ascorbic acid, 50 ¡¿I; catalase ( I mg/ml), 50 ¡¿I containing 1,500 units, and 0.4 M tyramine-HCI, 50 u.1.…”