Presence of free, sulfate and glucuronide conjugated 3-methoxy-4-hydroxyphenylglycol (MHPG) in human brain, cerebrospinal fluid and plasma.

The concentration of the free, glucuronide and the sulfate conjugated forms of 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured in human plasma, cerebrospinal fluid (CSF) and brain by mass fragmentography. All three forms of MHPG were detected in the media analyzed. Free MHPG was found to be the predominant form in both the brain and the CSF. The sulfate conjugate of MHPG constitutes about 15% of the total MHPG in the CSF while in the brain the percentage varies between 30% in the hypothalamus and cortex and 80% in the substantia nigra. The concentration of the glucuronide conjugate of MHPG measured in the brain and CSF represents about 5% of the total MHPG concentration. In the plasma free MHPG and its glucuronide and sulfate conjugates are present in about equal concentrations. The relative concentrations of the three forms of MHPG measured in plasma, CSF and brain were compared with their concentrations in the urine from previously published results. From this comparison the diagnostic significance of each of the three forms of MHPG in the clinical assessment of central norepinephrine metabolism is discussed.