title: Stimulatory role for endogenous opioid peptides on postexercise insulin secretion in rats.
abstract: Endogenous opioid peptides (EOP) and prior exercise may modulate the stimulatory effect of glucose on insulin secretion. To gain insights into these relationships, we studied male Wistar rats (187-245 g) during sustained hyperglycemia by use of the glucose clamp technique. Four groups of sedentary fed rats (n = 8/group) either ran (Ex) at 24 m/min, 0% grade, or rested (R) for 40 min. Thirty minutes after Ex or R, arterial blood glucose was elevated to and maintained at 11 mM for 2 h by a variable glucose infusion. At the start of Ex or R rats had saline (Sal) or naloxone (Nal, an opioid antagonist) intravenous infusions for 160 min (40 min Ex + 30 min R + 90 min of a 120-min glucose clamp). Steady-state glucose infusion rates (SSGIR) were approximately 55 mg.kg-1.min-1 at the start of the clamp and declined significantly over the 2nd h to approximately 45 mg.kg-1.min-1. No significant differences existed in SSGIR between groups. R-Sal and Ex-Sal groups did not differ in their insulin response to hyperglycemia. In contrast, when all groups were compared at the end of the Nal or Sal infusion, Ex-Nal had the lowest insulin concentration (749 +/- 174 pmol/l), whereas the R-Nal group had the highest (1,581 +/- 216 pmol/l, P less than 0.05). These data suggest a stimulatory role for EOP on insulin secretion that is expressed after a prior stress (Ex). Thus one function of exercise-induced activation of EOP may be to regulate insulin secretion in the immediate postexercise period.
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D004723:Endorphins / Q000502:physiology*; D004837:Epinephrine / Q000097:blood; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010805:Physical Conditioning, Animal; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001786:Blood Glucose; D004723:Endorphins; D007328:Insulin; D009638:Norepinephrine; D004837:Epinephrine