Action of epinephrine on the distribution of two model amino acids in the diabetic rat.

Abstract

The injection of epinephrine (1.0 mg/kg) into alloxan-diabetic, fasted rats depressed the serum concentration of previously administered α-aminoisobutyric acid (AIB) and 1-aminocyclopentanecarboxylic acid (ACPC) within 2 h and simultaneously increased the concentration of these amino acids in the liver. The increase of ACPC and AIB concentrations in the liver following epinephrine injection was nearly 3 times as great in the alloxan-diabetic rats as in normal intact rats. The levels of the two amino acids in skeletal muscle, heart, and diaphragm of the alloxanized rats were unchanged following epinephrine injection, but the distribution ratios in these tissues were raised because the serum concentration decreased 20%.Further studies were carried out employing rats that were treated 1 h before epinephrine injection, with mannoheptulose, a compound which blocks insulin release. The concentration of ACPC and AIB in the serum 2 h after epinephrine injection were lowered. At the same time the concentrations of ACPC in liver and heart were raised, as was the concentration of AIB in heart. The levels of the two amino acids in skeletal muscle and diaphragm were unaltered. However, distribution ratios were raised in the four tissues. These results demonstrate that epinephrine enhances AIB and ACPC transport into the tissues of the insulin-deficient rats <i>in vivo</i> and suggest that epinephrine-stimulated amino acid transport is not due indirectly to insulin.