Simultaneous evaluation of the catecholamine pathway and three opioid peptide-producing systems in human...

Tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) activities, dopamine (DA), noradrenaline (NA), adrenaline (A), met 5-enkephalin (Met-Enk), leu5-enkephalin (Leu-Enk), dynorphin (Dyn) and beta-endorphin (beta-end) were measured simultaneously in ten human pheochromocytomas = 1 - TH activity was highly variable, from 22 to 2220 U/g tissue. 2 - DBH activity, in contrast, was rather constant, from 96 to 582 U/g. 3 - Catecholamines (A and NA) concentrations showed only small variations. 4 - The four opioid peptides were detected in all cases and exhibited a wide range of tissue concentrations (Enk much greater than Dyn greater than beta-end). 5 - Met-Enk and Leu-Enk concentrations were highly correlated; no correlation was observed with the other opioid peptides. 6 - A very strong correlation was observed between enkephalins concentrations and both catecholamines concentrations and DBH activities. These results are discussed in term of the significance of the co-localization of these various biologically active substances, principally with regard to the possible regulation of catecholamine synthesis by opioid peptides and conversely.