Serum dopamine-beta-hydroxylase activity: sibling-sibling correlation.

Dopamine-beta-hydroxylase activity is released into the blood with catecholamines from the adrenal medulla and sympathetic nerves. This enzyme activity has been measured in the blood of 317 normal children and 227 normal adults. A significant sibling-sibling correlation of serum dopamine-beta-hydroxylase values was found in the 94 sibling pairs tested. Frequency distributions of serum enzyme values in both children and adults suggest the existence of two populations with regard to serum activity of this enzyme.