Sympathoadrenal activity during exercise in partial diabetic and diabetic rats

Insulin-dependent diabetes mellitus is associated with altered fat and carbohydrate metabolism and disturbed sympathoadrenal functioning. The aim of this study was to investigate whether the short-term diabetic state alters the activity of the sympathoadrenal system and of the adrenal cortex during exercise. In addition, the possible reciprocal effects of a deviating sympathoadrenal functioning and an altered non-esterified fatty acid (NEFA) and glucose metabolism were investigated. Therefore, control rats, diabetic rats, and partial diabetic rats were submitted to swimming (15 minutes). Permanent heart catheters allowed frequent blood sampling without disturbing the animals. Blood glucose and plasma NEFA levels increased during exercise. Partial dia betic animals showed similar effects as controls. In contrast, the glucose and NEFA increments were significantly higher in diabetic rats than in control and partial diabetic rats. During exercise, the very low insulin levels were unaltered in diabetic rats, whereas they decreased in the other groups. Exercise-induced elevations of plasma epinephrine and norepinephrine were similar in all groups, but were lower for corticosterone in the diabetic animals. Therefore, these results provide evidence that the exaggerated NEFA mobilization in diabetic rats is only the result of reduced inhibition of lipolysis by the relative lack of insulin. It is concluded that the short-term diabetic state does not alter the activity of the sympathetic nervous system during exercise, but lowers the activity of the adrenal cortex.