Abstract
The effect of adrenodemedullation (ADMX) on insulin action was examined in anesthetized rats by means of a three-step euglycemic clamp procedure (insulin infusion rate: 0, 6.0 and 30.0 mU•kgBW-1•min-1) combined with a microdialysis technique in skeletal muscle and adipose tissue. The dialysate lactate levels in the above tissues increased in parallel with the plasma lactate levels during the sequential euglycemic clamp. In the euglycemic clamp, the glucose infusion rate (GIR) was significantly (P<0.01) higher in ADMX rats (13.41±0.82mg•kgBW-1•min-1) than in SHAM rats (10.21±0.87 mg•kgBW-1•min-1) during the 6.0-mU•kgBW-1•min-1 insulin infusion, and the lack of a ignificant difference between ADMX and SHAM rats was observed during the 30-mU•kgBW-1•min-1 insulin infusion. In skeletal muscle, the concentration of lactate in dialysate was significantly higher in ADMX rats (9.29±1.01mg/dl) than in SHAM rats (6.22±0.47mg/dl) (P<0.05) at an insulin infusion rate of 6.0mU•kgBW-1•min-1. In adipose tissue, no significant difference in dialysate lactate levels was found between ADMX and SHAM rats at any insulin infusion rate. These results suggest that 1) it is possible to determine insulin action in skeletal muscle and adipose tissue in vivo by using the microdialysis technique, that 2) ADMX appears to result in a significant increase in insulin sensitivity, and that 3) lactate formation increased in skeletal muscle, but not in adipose tissue.
