Whereas TH levels were correlated with ERK5 levels in normal adrenal medullas, ERK5 was down-regulated and TH was up-regulated in pheochromocytomas, indicating that TH levels are regulated by alternative mechanisms in tumors.
We observed an increase of TH mRNA concentration without correlation with TH protein expression in primary cell culture of PHEO and PGL incubated with dexamethasone during 24 hours; no changes were monitored for PNMT and DBH at both mRNA and protein level in PHEO and PGL.
PACAP mRNA expression correlated with TH (p=0.0018) and PNMT (p=0.05) mRNA expression, as well as epinephrine (p=0.0342) levels in 16 intra-adrenal pheochromocytomas.
The above differences in clinical presentation were largely explained by lower total tissue contents of catecholamines and expression of TH and negligible stores of epinephrine and expression of PNMT in pheochromocytomas from VHL than from MEN 2 patients.
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.
Our findings suggest substantial differences in TH transcriptional rates or the stability of TH mRNA or both may contribute to altered TH expression in human chromaffin cells associated with "normal" adrenal tissues and various forms of pheochromocytoma and distinctive patterns of expression in the different settings in which these tumors arise.
We show that the diversity of TH mRNAs is greater than previously described in the autonomous nervous system: New splice junctions corresponding to the skipping of exon 3 were identified by amplification of cDNA synthesized from pheochromocytoma RNA.
Purification and characterization of the blue-green rat phaeochromocytoma (PC12) tyrosine hydroxylase with a dopamine-Fe(III) complex. Reversal of the endogenous feedback inhibition by phosphorylation of serine-40.