GLUCOREGULATORY HORMONES IN THE IMMOBILIZATION STRESS-INDUCED INCREASE OF PLASMA-GLUCOSE IN FASTED AND FED RATS

We investigated 1) the effect of immobilization stress on glucose meta bolism in rats after sham operation (SHAM), adrenomedullectomy (ADMX), and adrenalectomy (ADX); and 2) the effect of glucoregulatory hormone infusion on plasma glucose using untreated normal fasted and fed rats under unanesthetized conditions. In immobilization stress, the plasma glucose concentration increased only in the SHAM group during fasting , while under fed conditions, all three groups showed significant incr eases (SHAM > ADMX > ADX). Plasma glucagon and norepinephrine signific antly increased in all groups; plasma epinephrine increased only in th e SHAM group, and plasma corticosterone increased in SHAM and ADMX gro ups under both conditions. The hepatic glycogen content in all fed gro ups significantly decreased after immobilization stress, while a very low content before stress and an undetectable level after stress were observed in all fasted groups. Only epinephrine infusion increased pla sma glucose during fasting, while epinephrine and glucagon infusion in creased it under fed conditions. Corticosterone infusion did not chang e it under either condition. These results suggest that in the fasted condition, only epinephrine plays an essential role, while under fed c onditions, glucagon and corticosterone as well as epinephrine also act as synergistic factors in stress-induced hyperglycemia.