The impact of the absence of an increase in glucagon on the metabolic response to stress hormone infusion was investigated. We studied 11 conscious dogs fasted for 20 h before (day 0) and after (day 3) a 70-h stress hormone infusion containing glucagon, cortisol, epinephrine, and norepinephrine that increased their respective levels approximately sixfold. Five additional dogs were studied on day 0 and were then infused with the same stress hormone infusion but without glucagon. Glucose production and gluconeogenesis were assessed using tracer and arteriovenous difference techniques. The absence of an increase in glucagon during stress hormone infusion attenuated the increase in arterial plasma glucose concentration (delta 81 +/- 16 vs. delta 28 +/- 6 mg/dl) but did not significantly alter the increase in the rate of glucose appearance (delta 1.7 +/- 0.3 vs. delta 1.1 +/- 0.4 mg.kg-1.min-1). However, it eliminated the increase in net hepatic glucose output (delta 0.7 +/- 0.3 vs. delta 0.0 +/- 0.4 mg.kg-1.min-1) primarily because of an increase in hepatic glucose uptake. In addition, the stress hormone-induced increase in net hepatic gluconeogenic precursor uptake (delta 0.7 +/- 0.3 vs. delta 0.2 +/- 0.1 mg of glucose.kg-1.min-1) and the efficiency of gluconeogenesis (delta 0.19 +/- 0.07 vs. delta 0.01 +/- 0.05) were attenuated. Glucagon thus plays a pivotal role in the metabolic response to stress hormone infusion by sustaining gluconeogenesis through a stimulatory effect on the hepatic gluconeogenic precursor uptake as well as on the efficiency of gluconeogenesis within the liver.