NIH conference. Dopamine- -hydroxylase. Basic and clinical studies.

Dopamine-beta-hydroxylase, the enzyme responsible for conversion of dopamine to norepinephrine, is released along with catecholamines from the adrenal medulla and from sympathetic nerve endings. The properties and mechanisms of the enzyme's action are discussed and its distribution described. Dopamine-beta-hydroxylase is a valuable indicator of exocytosis as a mechanism for neurotransmitter release. The enzyme is present in plasma, but its levels vary widely between individuals. This variation seems to be related more to genetic factors than to sympathetic nerve activity. Abnormally high or low plasma levels are associated with several diseases. However, the relation of these levels to disease pathogenesis rather than to genetic determinants is unclear. Levels of the enzyme are elevated in patients with pheochromocytoma and decline after removal of the tumor. Dopamine-beta-hydroxylase levels seem to be normal in hypertensive patients. Inhibition of dopamine-beta-hydroxylase provides a useful pharmacologic approach to evaluating the role of norepinephrine in psychiatric disorders.