Fig. 4

Characterization of arginine transport in CHO cells. Panel a. CHO cells, seeded in 96-well plates, were washed in EBSS in the presence or absence of sodium, and arginine transport was measured through a 1-min incubation in the same solution containing L-[³H] arginine (0.05 mM; 2 μCi/ml) in the absence or presence of 2 mM leucine (+Leu) or 2 mM leucine + 2 mM lysine (+Leu + Lys) (see Methods). Data are means ± SEM of three different experiments, each performed in quadruplicate. Panel b. Data shown in Panel a were employed to calculate the relative contribution of systems y⁺L and y⁺: the first corresponds to the difference between total transport and transport measured in the presence of leucine, while the latter to the difference between transport observed in the presence of leucine and that measured in the presence of leucine+lysine. ** p < 0.01, *** p < 0.001 vs control (total, Na⁺ present)