To evaluate the effect of epinephrine on the circulating amino acids, we infused epinephrine into normal human subjects and juvenile-onset diabetic patients given a constant basal infusion of insulin. Epinephrine infusion produced an identical 350-400 pg/ml rise in plasma epinephrine in both groups. In normal subjects, epinephrine caused a progressive 26% reduction in total circulating amino acids, despite unchanged levels of plasma insulin. This effect was most pronounced for the branched amino acids, which fell by 40% (P < 0.001). Plasma alanine was the only amino acid which failed to decline. Similarly, infusion of epinephrine in the insulin-infused diabetics produced a 23% fall in total amino acids, a 37% decline in branched chain amino acids, but no change in plasma alanine. Saline infusion in the insulin-infused diabetics had no effect on plasma amino acid concentrations. In addition, when epinephrine was infused into two insulin-withdrawn diabetics, a comparable hypoaminoacidemic response was observed. The infusion of propranolol in both normal and diabetic subjects totally prevented the epinephrine-induced fall in plasma amino acids. It is concluded that (1) increments in epinephrine similar to those observed in stress cause a decline in circulating amino acids (except alanine) which is greatest for the branched chain amino acids; (2) this hypoaminoacidemic effect occurs in the absence of a rise in plasma insulin and diabetic subjects, as well; and (3) epinephrine-induced changes in amino acid regulation are prevented by β-adrenergic blockade. Our findings suggest that, in contrast with glucose and fat metabolism, epinephrine and insulin may have similar, rather than antagonistic, effects on plasma amino acid metabolism.
ASJC Scopus subject areas
- Internal Medicine
- Endocrinology, Diabetes and Metabolism