ADENOSINE INDUCES SYSTEM-A AMINO-ACID-TRANSPORT IN CULTURED RAT HEPATOCYTES

Adenosine caused a 2.5-fold increase in the sodium-dependent uptake of 2-aminoisobutyric acid in rat hepatocytes in primary culture following incubation for 3 h. The range of stimulating concentrations of adenosine corresponded to that of cAMP formation. Adenosine increased the V(max) of the transport without altering the K(m) for 2-aminoisobutyric acid. These effects of adenosine were abolished by actinomycin D. N6-L-Phenylisopropyladenosine also caused twofold increase in the amino acid transport. These findings suggest that adenosine induces System A amino acid transport in a transcription-dependent manner, and that P1-purinergic receptors are mainly involved in this action of the nucleoside.