Relation of Exercise to MHPG Excretion in Normal Subjects

Five normal subjects exercised for two hours on two of three consecutive days using isometric and isotonic exercise procedures. Urinary levels of norepinephrine (NE), normetanephrine (NM), metanephrine (M), and urine and plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured for the two-hour periods before, during, and after exercise. A ten-fold increase in urinary NE levels was Present after both exercise procedures. No increase in urinary levels of MHPG or M was observed during or two hours after exercise. Slight increases of plasma MHPG levels and urinary NM levels were observed during one of the two exercise periods compared to the two hours preceding exercise. Since urinary MHPG, NM, and M levels did not parallel the large increase in NE levels produced by exercise, it is probable that the NE produced by exercise is largely excreted or removed from circulation without metabolic breakdown. Thus, changes in urine MHPG levels in Patients with affective psychoses are not likely to be due to variations in the amounts of isotonic or isometric motor activity.