Low serum dopamine beta-hydroxylase activity. A marker of congestive heart failure

To gain information about the nature of disturbances in sympathetic nervous system control in congestive heart failure, serum dopamine beta-hydroxylase (DBH) activity was measured in 30 patients with heart failure of diverse etiologies and 29 healthy normotensive controls. The heart failure patients had been symptomatic for at least 6 wk and had elevated filling pressures, low cardiac indices, low ejection fractions, and wide arteriovenous oxygen differences. DBH activity was 47.1+/-4.7 (mean+/-SE) for the controls and 14.4+/-2.7 IU for the heart failure patients (P < 0.001). Sera from some patients with heart failure had potent inhibitory effects on DBH activity of normal sera. The inhibitor was heat stable and dialyzable and could be demonstrated despite presence of N-ethylmaleimide or Cu(++) in the reaction mixture. However, some inhibitory activity was also present in sera of normal patients; this inhibitory property was not demonstrable in unheated normal serum, but was unmasked when DBH was heat inactivated. It is proposed that although the inhibitor may have been a factor in low serum DBH activity in some patients with heart failure, the major cause of the low activity in the heart failure group was a reduced rate of synthesis or release of the enzyme by sympathetic nerves. This may reflect a dissociation between rates of neural release of norepinephrine and release of DBH in chronic, severe heart failure. The observation of low serum DBH levels in patients with heart failure suggests that measurement of DBH levels may serve as a useful indicator of cardiac dysfunction.