Direct measurement of active transport systems for alanine in freshly isolated rat liver cells

A method for the direct measurement of alanine transport in liver cells has been developed with the use of alanine aminotransferase inhibitors which block the metabolic utilization of alanine. Freshly isolated rat hepatocytes treated with DL-cycloserine or aminooxyacetate are shown to actively accumulate alanine by three neutral amino acid transport systems, analogous to the A, ASC, and L systems of Ehrlich ascites tumor cells. At a medium concentration of 1mM, these systems contribute 60, 20, and 5% respectively to hepatic alanine uptake. Passive influx accounts for the remainder.