Effects of Treadmill Exercise on Insulin Secretion in Rats

Journal of Exercise Nutrition & Biochemistry 1997;1(2):37-48.

Abstract

The purpose of this study was to investigate the effects of exercise upon insulin secretion through male Sprague-Dawlay rats. That is to say, it was to determine whether exercise reduces insulin secretion or not. The rats were randomly divided into seven exercise-trained rats(SG) and seven sedentary rats(SG), and EG was subjected to a six weeks physical training by means of treadmill running four days per week. The experiment on EG was carried out in the state of overnight fast forty-eight hours after the exercise in order to eliminate the effect of the last bout of the exercise. This study was successively performed by three stages to find out insulin secretion response to stimuli for 130 minutes. At first, arginine bolus was injected in basal level, and insulin secretion response to arginine stimulus was evaluated 40 minutes after the injection. Next, hyperglycemic clamp procedure was introduced for 20 minutes, and insulin secretion response to glucose stimulus was evaluated Finally, arginine was additionally infused in the state of a hyperglycemic clamp(stage 2), and insulin secretion response to synergism of both glucose and arginine stimuli was evaluated. The results were as follows. When arginine bolus was injected in basal level, plasma insulin concentration in EG was lower than that in SG. Secretory response of insulin in EG during hyperglycemic clamp was lower than that in SG. When arginine was additionally injected in the state of a hyperglycemic clamp, plasma insulin concentration in EG was lower than that in SG. From the above results, the reduced plasma insulin concentrations in response to these stimuli in EG could be explained either by a blunted sensitivity of the β-cell or by a reduced capacity of the β-cell tp secrete insulin in vivo.