Insulin and glucagon immunoreactivity during high-intensity exercise under opiate blockade.
Eight fit men [maximum oxygen consumption (VO2max) 64.6 (1.9) ml x kg(-1)xmin(-1), aged 28.3 (1.7) years (SE in parentheses) were studied during two treadmill exercise trials to determine the effect of endogenous opioids on insulin and glucagon immunoreactivity during intense exercise (80% VO2max). A double-blind experimental design was used with subjects undertaking the two exercise trials in counterbalanced order. Exercise trials were 20 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration of naloxone (N; 1.2 mg; 3 ml) and the other after receiving a placebo (P; 0.9% NaCl saline; 3 ml). Prior to each experimental trial a flexible catheter was placed into an antecubital vein and baseline blood samples were collected. Immediately after, each subject received either a N or P bolus injection. Blood samples were also collected after 20 min of continuous exercise (running). Glucagon was higher (P < 0.05), while insulin was lower (P < 0.05), during exercise compared with pre-exercise values in both trials. However, glucagon was higher (P < 0.05) in the P than in the N exercise trial [141.4 (8.3) ng x 1(-1) vs 127.2 (7.6) ng x 1(-1)]. There were no differences in insulin during exercise between the P and N trials [50.2 (4.3) pmol x 1(-1) vs 43.8 (5) pmol x 1(-1)]. These data suggest that endogenous opioids may augment the glucagon response during intense exercise.
Angelopoulos
T J
TJ
Laboratory of Applied Physiology, The University of Southern Mississippi, Hattiesburg 39406, USA.
Robertson
R J
RJ
Goss
F L
FL
Utter
A
A
D000328:Adult; D015444:Exercise / Q000502:physiology*; D005934:Glucagon / Q000187:drug effects* / Q000378:metabolism; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008297:Male; D009270:Naloxone / Q000494:pharmacology*
D007328:Insulin; D009270:Naloxone; D005934:Glucagon