THE EFFECT OF LESIONS OF THE SYMPATHOADRENAL SYSTEM ON TRAINING-INDUCED ADAPTATIONS IN ADIPOCYTES AND PANCREATIC-ISLETS IN RATS

Physical training increases insulin stimulated glucose uptake in adipo cytes and decreases insulin secretion from pancreatic islets. The mech anism behind these adaptations is not known. Because in acute exercise adrenergic activity influences both adipocytes and pancreatic islets, the sympathetic nervous system was examined as the possible mediator. Rats were either adrenodemedullated or sham adrenodemedullated and un derwent either unilateral abdominal sympathectomy or were sham sympath ectomized. Resting plasma adrenaline concentration in adrenodemedullat ed rats was 32% of the concentration in sham adrenodemedullated rats ( P < 0.0001) and muscle noradrenaline content in sympathectomized leg w as 9% of content in sham sympathectomized leg (P < 0.0001). Alter oper ations rats were either swim trained for 10 weeks or remained sedentar y. Insulin stimulated 3-O-[C-14]methylglucose transport was measured i n adipocytes from epididymal fat pads. and insulin secretion and gluco se metabolism were measured in glucose stimulated pancreatic islets. T raining increased insulin stimulated glucose transport in adipocytes ( P < 0.0001) and decreased their size (P < 0.0001), but neither adrenod emedullation nor sympathetic denervation affected these parameters sig nificantly. Training decreased insulin secretion (P < 0.01) and increa sed glucose oxidation (P = 0.02) and utilization (P = 0.08) in pancrea tic islets, but none of these parameters was affected significantly by adrenodemedullation. It is concluded that adrenergic activity is not important for the training induced decrease in size and increase in in sulin stimulated glucose transport of adipocytes. Neither is an intact adrenal medulla necessary for training-induced adaptations in pancrea tic beta cell function. Finally. in response to training. P cell insul in secretion and glucose metabolism changed in opposite directions.