Da. Fryburg et al., EFFECTS OF EPINEPHRINE ON HUMAN MUSCLE GLUCOSE AND PROTEIN-METABOLISM, American journal of physiology: endocrinology and metabolism, 31(1), 1995, pp. 55-59
Systemic epinephrine infusion causes hypoaminoacidemia and inhibits wh
ole body leucine flux (proteolysis) in humans. Its specific action on
muscle protein is not known and is difficult to assess during systemic
epinephrine infusions, which affect plasma insulin, amino acid, and f
ree fatty acid concentrations. During a steady-state infusion of L-[ri
ng-2,6-H-3] phenylalanine, we examined the effect of locally infused e
pinephrine on the metabolism of protein and glucose in forearm muscle
of 10 healthy human volunteers. During local epinephrine infusion, sys
temic concentrations of glucose, phenylalanine, insulin, and epinephri
ne were unchanged and lactate declined (P < 0.02). Compared with basel
ine, epinephrine induced significant increases in forearm blood flow (
P < 0.01) and net lactate release (P < 0.001) and a decrease in glucos
e uptake (P < 0.01) at both 2 and 4 h. At 2 and 4 h phenylalanine rele
ase from muscle proteolysis was suppressed (P < 0.01), and at 4 h the
net phenylalanine balance was less negative than baseline (P < 0.02),
indicating an anticatabolic effect on muscle protein. We conclude that
in human forearm muscle epinephrine, at physiological concentrations,
has a catabolic effect on muscle glycogen but an anticatabolic action
on muscle protein. The mechanism of this latter effect is not known.