Dopamine-β-hydroxylase (DBH), the enzyme responsible for the bio
synthesis of norepinephrine from dopamine was assayed in the blood serum
of 23 normal adults, 16 patients with congestive heart failure, 19 patients
with asymptomatic ischemic heart disease, 4 patients with angina pectoris
at rest, 15 patients with essential hypertension, 8 patients with essential
hypotension, 5 patients with neurocirculatory asthenia, and 9 normal adults
before and after the exercise test. The serum DBH activity varied within
a wide range in the control population. The DBH activity increased
about 16% after the exercise stress. A tendency to increase DBH activity
was shown in the patients with congestive heart failure. There was no
significant difference between asymptomatic ischemic heart disease, es
sential hypertension and normal controls. A lower value was observed
in the patients of angina pectoris at rest, while a higher DBH activity
was demonstrated in the patients with essential hypotension. There was
no significant difference between the neurocirculatory asthenia group and
the normal control group.