OBJECTIVE: To understand the molecular mechanisms by which catecholamine 
synthesis is controlled in pheochromocytomas--tumors that synthesize and release 
catecholamines, which are related to various clinical manifestations of the 
condition.
METHODS: We measured the concentrations of mRNA coding for the 
catecholamine-synthesizing enzymes tyrosine hydroxylase, aromatic L-amino acid 
decarboxylase (AADC), dopamine beta-hydroxylase (DBH) and phenylethanolamine 
N-methyl transferase (PNMT) and for the catecholamine contents in 12 
pheochromocytomas and 12 normal adrenal medullas.
RESULTS: The mean content of total catecholamine and the beta-actin mRNA 
expression in the pheochromocytomas were almost the same as those in the normal 
adrenal medullas. However, the tyrosine hydroxylase, AADC and DBH mRNA 
concentrations in the pheochromocytomas were greater than those of the normal 
adrenal medullas. Conversely, the PNMT mRNA concentration in the 
pheochromocytomas was lower than that in the normal adrenal medullas. These 
differences are responsible for the difference in the proportions of 
catecholamines between pheochromocytomas and normal adrenal medullas. The 
constitutive expression of the catecholamine-synthesizing enzyme mRNAs varied in 
magnitude among the pheochromocytomas, and the tyrosine hydroxylase mRNA 
expressions correlated with the contents of total catecholamine in the tumors 
(r=0.964, P<0.0001).
CONCLUSIONS: These findings indicate that catecholamine production in 
pheochromocytomas is primarily controlled by the level of gene expression.