Dopamine-beta-hydroxylase in patients with cystic fibrosis

The enzymatic activity of plasma dopamine-beta-hydroxylase (DBH) was determined in 92 children/adolescents with cystic fibrosis, in 25 parents (heterozygotes) of these patients and in 68 healthy controls. Statistically significant (P<0.01) lower DBH levels were found in cystic fibrosis patients (17.9±1.4 μmol/min per 1, SEM) compared to the controls (25.5±2.1 μmol/min per 1). In 37 patients plasma norepinephrine and dopamine levels were compared to the enzymatic activity, no significant correlation between these variables being shown (r=-0.134 for norepinephrine; r=0.159 for dopamine). However, due to the large variability of DBH within the groups and due to the lack of relationship of this enzymatic activity to plasma catecholamines, it is concluded that these differences may neither account for the observed elevation of plasma dopamine in cystic fibrosis patients (0.94–6.73 nmol/l vs. 0.01–0.986 nmol/l for controls) nor for their putative autonomic dysfunction.