It has been suggested that cerebral noradrenaline turnover in patients can be assessed from the excretion in urine of 3-methoxy-4-hydroxyphenylethylene glycol (MOPEG). Studies were therefore made on the effects of mild exercise on the excretion of the conjugates of MOPEG as this might complicate interpretation. Changes are produced, but there are individual differences between subjects.
Physical fitness was also studied and, although it could not be shown to be the factor explaining differences between different patients, nevertheless it is probably a factor influencing the levels of MOPEG excreted.
The study of the distribution of free MOPEG and its sulphate conjugate in a human brain also raised doubts about the proportions which could have a cerebral origin.
The observations suggest the need for caution in using MOPEG excretion to detect abnormal amine changes in brain. They do not, however, conclusively refute the hypothesis that MOPEG sulphate in urine significantly reflects cerebral noradrenaline activity.