Fig. 1: Endogenous contributions to leucine transport in the B⁰AT1 flux assay.

L-leucine transport was characterized in CHO-BC cells using uptake of 150 µM L-[¹⁴C]leucine. a Uptake of L-leucine was measured in the presence (yellow) and absence (green) of Na⁺. An apparent increase of Na⁺-independent leucine transport is observed after application of increasing concentrations of B⁰AT1 inhibitor cinromide. L-Leucine transport is blocked incompletely due to endogenous transport activities. b The Na⁺-independent endogenous transport can be blocked by LAT1 inhibitor JPH203. The Na⁺-dependent component of L-leucine uptake that is sensitive to inhibition by GPNA (γ-glutamyl-p-nitroanilide) was assigned to ASCT2. The remaining transport activity was assigned to B⁰AT1. Transport components are indicated by colour. c In the presence of GPNA (3 mM) and JPH203 (3 µM), the remaining Na⁺-dependent transport activity is completely blocked by cinromide. (d) IC₅₀ of cinromide as determined with the optimized assay. All data shown as mean ± SD, individual datapoints were overlayed in all bar graphs (n = 3, n referring to individually seeded cell culture dishes used for each condition or concentration).