Diminished glucagon response to epinephrine in physically trained diabetic rats

The effect of physical training on glucose, insulin, and glucagon response to epinephrine was assessed in normal and diabetic rats. Male Wistar rats were injected with streptozocin (STZ, 45 mg/kg) and those presenting 1 wk later a blood glucose value between 250 and 400 mg/dl were retained in the protocol and randomly assigned to a sedentary or trained group. Similar studies were conducted in control animals. Physical training was done on a treadmill according to a 10-wk program. Epinephrine (0.75 microgram/kg/min) was infused intravenously (i.v.) in previously cannulated rats for 1 h and arterial blood samples obtained at 15-min intervals for glucose, insulin, and glucagon measurements. Pancreatic insulin and glucagon content was also determined. Basal glucose levels were significantly lower in trained than in sedentary diabetic rats (P less than 0.01). The hyperglycemic response to epinephrine was diminished by 19% and 23% in trained control and diabetic animals, respectively, with a faster return to baseline after stopping epinephrine infusion in both trained groups. Although in nondiabetic rats this could be related to some diminution in the suppressive effect of epinephrine on insulin secretion, this was not the case in diabetic animals. Moreover, while training did not modify epinephrine-induced glucagon response in control rats, the twofold greater (P less than 0.01) glucagon response observed in sedentary diabetic rats was restored to normal in trained diabetic rats. After stopping epinephrine infusion, glucagon levels dropped below the baseline in both groups of trained rats but not in their sedentary counterparts. These effects of training on glucagon response could not be explained by changes in pancreatic glucagon content.(ABSTRACT TRUNCATED AT 250 WORDS)