The 4- O-Methylation pathway of catecholamines: Search for an in vivo production of 3-hydroxy,4-methoxyphenylglycol(iso-MHPG)

The existence of 3-hydroxy,4-methoxyphenylglycol in biological fluids has been investigated. 4-Hydroxy,3-methoxy-phenylglycol (MHPG) and 3-hydroxy,4-methoxyphenylglycol (iso-MHPG) have been separated from each other by gas-liquid chromatography of their heptafluorobutyryl derivatives, using an electron capture detector procedure. Urines of normal subjects, of patients with secreting nervous tissue tumors and human cerebrospinal fluids were analyzed. Iso-MHPG was never detected, with the exception of trace amounts in one urinary sample from a patient with a peculiarly high excretion of MHPG. It is concluded that norepinephrine is probably not 4- O-methylated in vivo, contrary to dopamine which is known to lead, at least to a small extent, to 4- O-methylated metabolites.