Effect of Adrenaline on Amino Acid Transport in Perfused Rat Heart

Effects of adrenaline on amino acid transport in the isolated perfused rat heart was investigated using the non‐utilizable amino acidsα‐aminoisobutyric acid (AIB) and 1‐aminocyclopentanecarboxylic acid (cycloleucine). Adrenaline, addedin vitro, caused a dose dependent increase in the uptake of AIB and cycloleucine, and a significant stimulation was seen after 15 min of perfusion. The minimal effective concentration was 5 × 10‐8M, and an effect was obtained when hearts were perfused with glucose or palmitate as substrate and when no exogenous substrate was added. Adrenaline increased the uptake in hearts arrested with high [K+] or tetrodotoxin, and the accelerated uptake was not dependent upon the chronotropic effect of adrenaline. Under conditions when adrenaline increased amino acid uptake, protein synthesis was either unaffected or decreased. The data of the present study show that adrenaline directly stimulates amino acid transport in the heart and it is concluded that increased uptake of amino acids could be an energy‐generating system for the heart during adrenergic stimulation.