Figure 4.

Time course (A) and characterization (B) of ¹⁴C-l-methionine (¹⁴C-l-Met) uptake by Bewo cells. For time course experiments, the cells were incubated for various periods of time at 37°C with 250 nmol/L ¹⁴C-l-Met, at pH 7.5 (n = 8). Analysis of the time course allowed the determination of the steady state accumulation (A _max) and the rate constant for inward (k _in) and outward (k _out) transport. For the characterization experiments, initial rates of uptake were determined in cells incubated at 37°C with 250 nmol/L ¹⁴C-l-Met for 6 minutes in the absence (control; corresponding to 100%) or in the presence of 1 mmol/L 2-amino-2-norbornanecarboxylic acid (BCH), 100 µmol/L l-Phe, 100 µmol/L l-Trp, 100 µmol/L d-Leu, 100 µmol/L d-Phe, 100 µmol/L l-Ser, 100 µmol/L l-Ala, 100 µmol/L l-Lys, 100 µmol/L l-Arg, or 1 mmol/L α-(methylamino)isobutyric acid (MeAIB; n = 6-12). Shown is arithmetic mean ± standard error of the mean. *Significantly different from control (P < .05).