Relationship between the activity of plasma dopamine-beta-hydroxylase and the duration of diabetes mellitus.

Plasma DBH activity was studied in a group of 50 normal individuals, a group of 53 diabetics diagno sed less than 2 years ago (01) and a group of 49 diabetics diagnosed more than 10 years ago (02). The enzyme activity was significantly different in the 2 groups, 01 having the lower activity and G2 the highest. We interpret our results accepting that in G1 the damage of noradrenergic terminals allows less DBH to be liberated to the blood, whereas in 02 DBH reuptake by damaged sympathetic nerves is the predominant lesion, having as a result a prolonged persistence of the enzyme in the plasma.