Desensitization of the inhibitory effect of norepinephrine on insulin secretion from pancreatic islets of exercise-trained rats.

The effect of exercise training (9 weeks of running) on norepinephrine-induced inhibition of insulin secretion was examined in rat islets. Insulin secretions from islets in the presence of glucose (> or =5.5 mmol/L) were significantly lower in trained (TR) than in control rats (CR).

Enhanced expression of neuronal nitric oxide synthase in islets of exercise-trained rats.

It is well known that glucose-stimulated insulin secretion (GSIS) decreases after exercise training. In the present study, we investigated the effects of exercise training (9 weeks of running) on the activity of glucokinase (GK), the production of nitric oxide (NO), and the protein expressions of both glucose transporter-2 (GLUT-2) and NO synthase (NOS) in rat pancreatic islets. Exercise training significantly reduced GSIS, with decreases in GK activity and GLUT-2 protein expression.