ROLE OF EPINEPHRINE AND NOREPINEPHRINE IN THE METABOLIC RESPONSE TO STRESS HORMONE INFUSION IN THE CONSCIOUS DOG

The role of epinephrine and norepinephrine in contributing to the alte rations in hepatic glucose metabolism during a 70-h stress hormone inf usion (SHI) was investigated in four groups of chronically catheterize d (20-h-fasted) conscious dogs. SHI increased glucagon (similar to 5-f old), epinephrine similar to 10-fold), norepinephrine (similar to 10-f old), and cortisol (similar to 6-fold) levels. Dogs received either al l the hormones (SHI; n = 5), all the hormones except-epinephrine (SHI- Epi; n = 6), or all the hormones except norepinephrine (SHI-NE; n = 6) . In addition, six dogs received saline only (Sal). Glucose production (R-a) and gluconeogenesis were assessed after a 70-h hormone or salin e infusion with the use of tracer ([3-H-3]glucose and [U-C-14]alanine) and arteriovenous difference techniques. SHI increased glucose levels (108 +/- 2 vs. 189 +/- 10 mg/dl) and R-a (2.6 +/- 0.2 vs. 4.1 +/- 0.3 mg.kg(-1).min(-1)) compared with Sal. The absence of an increase in e pinephrine markedly attenuated these changes (glucose and R-a were 140 +/- 6 mg/dl and 2.7 +/- 0.4 mg.kg(-1).min(-1), respectively). Only 25 % of the blunted rise in R-a could be accounted for by an attenuation of the rise in net hepatic gluconeogenic precursor uptake (0.9 +/- 0.1 , 1.5 +/- 0.1, and 1.1 +/- 0.2 mg.kg(-1).min(-1) for Sal, SHI, and SHI -Epi, respectively). The absence of an increase in norepinephrine did not blunt the rise in arterial glucose levels, R-a, or net hepatic glu coneogenic precursor uptake (they rose to 195 +/- 21 mg/dl, 3.7 +/- 0. 5 mg.kg(-1).min(-1), and 1.7 +/- 0.2 mg.kg(-1).min(-1), respectively). In summary, during chronic SHI, the rise in epinephrine exerts potent stimulatory effects on glucose production principally by enhancing he patic glycogenolysis, although the rise in circulating norepinephrine has minimal effects.