B-Endorphin and Natural Killer Cell Cytolytic Activity During Prolonged Exercise. Is There a Connection?


  1. Gannon, G.A.
  2. Rhind, S.G.
  3. Suziu, M.
  4. Zamecnik, J.
  5. Sabiston, B.H.
  6. and others
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
This study was designed to test whether a single 50-mg dose of the opioid antagonist naltrexone hydrochloride, ingested 60 min before 2 h of moderate-intensity exercise (i.e., 65% peak 02 consumption), influenced the exercise-induced augmentation of peripheral blood natural killer cell cytolytic activity (NKCA). Ten healthy male subjects were tested on four occasions separated by intervals of at least 14 days. A rested-state control trial was followed by three double-blind exercise trials (placebo (P), naltrexone (N), and indomethacin) arranged according to a random block design. The indomethacin exercise trial is discussed elsewhere (S.G. Rhind, G.A. Gannon, P.N. Skek, and R.J. Shepherd. Med. Sci. Sports Exerc. 30:S20, 1998). For both the P and N trials, plasma levels of Beta-endorphin were increased (P<0.50) at 90 and 120 min of exercise but returned to resting (preexercise) levels 2 h postexercise. CD3(-)CD16(+)CD56(+) NK cell counts and NKCA were significantly (P<0.05) elevated at each 30-min interval of exercise compared with correspondingly timed resting control values. However, there were no differences in NK cell counts or NKCA between P and N trials at any time point during the two trials. Changes in NKCA reflected mainly changes in NK cell count (r = 0.72;P<0.001). TRUNCATED
Immune suppression;Natural killer cells;Immune system;Immune function;Immune response;Cell adhesion;Growth hormone;Cortisol;Naltrexone;Natural immunity
Report Number
DCIEM-98-P-38 — Paper
Date of publication
08 Sep 1999
Number of Pages
Hardcopy;Document Image stored on Optical Disk

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