EFFECT OF HEPATIC VAGOTOMY ON PLASMA-CATECHOLAMINES DURING EXERCISE-INDUCED HYPOGLYCEMIA

The existence of a hepatosympathetic reflex active during insulin-indu ced hypoglycemia has recently been reported. The purpose of the presen t investigation was to test the hypothesis that the liver, through the afferent innervation of the vagus nerve, contributes to plasma epinep hrine and norepinephrine responses during exercise-induced hypoglycemi a. Hepatic vagotomized and sham-operated rats were killed at rest or a fter 30, 60, and 120 min of running exercise (26 m/min, 0% grade). At the end of the 120-min exercise period, liver glycogen, glucose, and i nsulin levels measured in the portal and peripheral plasma were all si gnificantly reduced (P < 0.05) while epinephrine and norepinephrine co ncentrations, beta-hydroxybutyrate, lactate, and portal and peripheral glucagon plasma levels were all significantly increased (P < 0.05). H owever, no significant differences were observed between hepatic vagot omized and sham-operated rats at rest and after exercise for the metab olic and hormonal responses. These results suggest that if a hepatosym pathetic reflex is active during an exercise-induced hypoglycemia situ ation, then this contribution is probably hidden by more important reg ulatory mechanisms.