Regulation of amino acid transport system L by amino acid availability in CHO-K1 cells. A special role for leucine

Abstract

Starvation of CHO-K1 cells for leucine leads to a 3-4-fold increase in transport system L activity, without modification of transport through systems A and ASC. The concentration of leucine must be below 10 [mu]M before the enhancement of transport can be clearly seen. To achieve low concentrations of leucine such as 10 [mu]M, extensive dialysis of fetal calf serum was required. The enhancement of transport was completed after 12-24 h of starvation and was fully reversed within 1 h of re-feeding with leucine. Starvation for isoleucine, valine or phenylalanine also produced an increase in system L transport activity, but the effect was only one half of that seen following leucine starvation.