Dopamine-beta-hydroxylase and its apparent endogenous inhibitory activity in the plasma of some psychiatric patients.

The "apparent" and "absolute" levels of dopamine-beta-hydroxylase (DBH) in 62 psychiatric patients and 20 healthy control subjects have been investigated. No significant differences could be detected between control subjects and patients diagnosed as schizophrenic, unipolar depressive and bipolar depressive, when DBH was assayed in the presence of the anti-inhibitors Cu++ and N-ethylmaleimide (i.e., "absolute" DBH activity). In the absence of these anti-inhibitors, however, the levels of plasma DBH (i.e., "apparent" DBH activity) were considerably reduced in all cases, with the schizophrenic group also being significantly reduced (p less than 0.02) in comparison with the control group.