Abstract
To elucidate whether increased plasma levels of free dopamine (F-DA) after exercise are due to deconjugation of sulfoconjugated (S-) DA in plasma, we compared the changes in plasma F- and S-DA, as well as changes in both the S- and F- forms of epinephrine (E) and norepinephrine (NE), after running a half-marathon. Free catecholamines (F-CAs) were measured by automated high-performance liquid chromatography (HPLC). Total (F+S) CAs were determined using an efficient deconjugation method as follows; 1200μl plasma was incubated with 152mU arylsulfatase (AS) for 30min at pH 7.6. The plasma levels of F-CA (pg/ml) (mean±SEM) all increased significantly (p<0.01) after the half-marathon: i.e., F-DA increased from 13.3±5.7 to 176.3±32.2; F-E from 58.0±12.3 to 764.3±136.4; F-NE from 246.6±15.2 to 3082.0±690.3. Of S-CAs, S-E (from 127.8±26.0 to 1218.2±190.8) and S-NE (from 717.1±61.6 to 5586.9±761.9) also increased, but, in contrast, among the S-CAs, only the increase in S-DA (from 5324.9±1967.3 to 7359.6±1627.9) was not statistically significant. Sulfoconjugation may play an important role in inactivating F-DA as well as F-NE and -E, that are released into plasma in response to vigorous exercise. Thus, plasma F-DA is unlikely to be derived through deconjugation of plasma S-DA. (Hypertens Res 1995; 18 Suppl. I: S161-S163)
