Total plasma dopamine/norepinephrine ratio in catecholamine-secreting tumors. Its relation to hypertension.

We used a radioenzymatic method to determine plasma levels of free and total (free plus sulfoconjugated) norepinephrine and dopamine in 20 children with neuroblastoma (two were hypertensive), seven patients with pheochromocytoma, and 39 normotensive controls (24 children and 15 adults). No significant differences were noted between the two control groups. Patients with neuroblastoma and pheochromocytoma showed significantly higher levels of free and total norepinephrine than controls (p less than 0.01), and those with pheochromocytoma had higher levels than those with neuroblastoma (p less than 0.01). Although the differences were not statistically significant, free dopamine was higher in both groups of patients than in controls. Total dopamine was significantly higher in patients than in controls (p less than 0.01). A positive correlation was noted between levels of total norepinephrine and total dopamine in controls (r = 0.41, p less than 0.05) and in patients with neuroblastoma (r = 0.72, p less than 0.001). Such a correlation was not found in patients with pheochromocytoma. The total dopamine/total norepinephrine ratio was higher (p less than 0.005) in patients with neuroblastoma than in controls and patients with pheochromocytoma. Patients with pheochromocytoma had significantly lower ratios than the other groups (p less than 0.001). A negative correlation was found between the ratios in the different groups and either systolic (p less than 0.001) or diastolic (p less than 0.001) blood pressure. Our results not only support a role for plasma dopamine in the regulation of blood pressure but also suggest that, regardless of the actual levels of both catecholamines, a balance has to be achieved in order to maintain normal blood pressure levels.