The effect of acute glucagon removal on the metabolic response to stress hormone infusion in the conscious dog.

The effect of acute glucagon removal on glucose metabolism following long-term (70-hour) stress hormone infusion (day 3) was investigated in 20-hour-fasted conscious dogs. Stress hormone infusion increased arterial plasma glucagon, cortisol, epinephrine, and norepinephrine (approximately fivefold), as well as arterial plasma glucose (delta 82 +/- 16 mg/dL) and insulin (delta 26 +/- 5 microU/mL). After assessing basal glucose metabolism on day 3, the long-term glucagon infusion was discontinued (n = 6), and the remaining hormones were infused for an additional 180 minutes. Constant glycemia was maintained by an exogenous glucose infusion. In five dogs, the stress hormone infusion containing glucagon was continued for 180 minutes. Glucose production and gluconeogenesis were assessed using tracer and arteriovenous-difference techniques. Acute removal of glucagon decreased arterial plasma glucagon from 220 +/- 24 to 32 +/- 4 pg/mL and net hepatic glucose output (delta 1.6 +/- 0.3 mg/kg/min). Net hepatic handling of lactate, alanine, and glycerol was not altered. The efficiency of gluconeogenesis, on the other hand, was decreased by 40%. Liver biopsies taken following discontinuation of glucagon indicated that both 3H- and 14C-glucose accumulated in glycogen. The calculated rate of plasma glucose and gluconeogenic precursor diversion to glycogen increased by fivefold and fourfold, respectively. The increased gluconeogenic precursor diversion to glycogen accounted for 58% of the decrease in the efficiency of gluconeogenesis. In conclusion, acute removal of glucagon during stress hormone infusion decreased net hepatic glycogenolysis in the face of prevailing hyperglycemia and hyperinsulinemia, while having minimal effects on the gluconeogenic process per se.