Beta-endorphin and ACTH in plasma: effects of physical and psychological stress.

The effects of the expectancy of an official race (22000 m) and the performance of this last event on plasma levels of beta-Endorphin (B-End) and ACTH have been assessed. In a group of nine athletes, samples were obtained first in basal conditions; second in the day of the run before the warming up period and third after running. B-End immunoactivity was increased from 15.7 +/- 2.0 pg/ml to 23.4 +/- 2.5 pg/ml before the run and up to 30.6 +/- 2.9 pg/ml after the trial. ACTH levels were increased from 8.4 +/- 1.2 pg/ml to 17.9 +/- 2.3 pg/ml before running and up to 36.2 +/- 3.9 pg/ml after running. The results suggest that psychological and physical stress act synergically to increase the levels of B-End and ACTH during the practice of physical exercise.