title: Plasma endorphin species during dynamic exercise in humans.
abstract: beta-Endorphin is metabolized to gamma- and alpha-endorphin. In order to evaluate endorphin metabolism during exercise, radioimmunoassay blood levels of alpha-, beta- and gamma-endorphins were recorded during exercise for 2 h on a cycling ergometer in 12 endurance-trained and 11 untrained male subjects. In untrained subjects, mild exercise (49 +/- 4% VO2max, mean +/- SD) did not show an increase in plasma beta-endorphin, while the levels of its metabolites rose. No changes were noted in the endurance-trained subjects. More intensive exercise (66 +/- 6% VO2max in untrained and 57 +/- 7% VO2max in trained subjects) resulted in an increase in beta-endorphin concentration in association with elevation of the alpha-endorphin level. While before and during exercise the beta-endorphin levels did not differ significantly between athletes and untrained subjects, the levels of gamma- and alpha-endorphins, as well as the molar ratios alpha/beta and gamma/beta, were significantly higher in untrained subjects. In conclusion, blood levels of beta-endorphin metabolites in the resting state and during exercise are dependent on previous training. In untrained subjects, mild exercise may result in accumulation of gamma- and alpha-endorphins in blood without a concomitant change in beta-endorphin level.
authors.affiliation: Institute of Exercise Biology, University of Tartu, Estonia.
authors.forename: A
authors.initials: A
authors.lastname: Viru
authors.forename: Z
authors.initials: Z
authors.lastname: Tendzegolskis
mesh_terms: D000328:Adult; D004723:Endorphins / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male
chemical_list: D004723:Endorphins