Fig. 3.

The effect of preincubation on the inhibition of OSTα/β-mediated transport of probe substrates. OSTab and Mock cells were preincubated with inhibitor (100 µM) for 10 min (Method 1, black), co-incubated with inhibitor and substrate during the uptake phase (Method 2, grey), or both preincubated and co-incubated, as described for Methods 1 and 2 (Method 3, white); the probe substrate, [³H]-dehydroepiandrosterone sulfate (DHEAS) or [³H]-taurocholate (TCA) (300 nCi/ml; 20 µM final concentration; 30 s uptake), was added in extracellular fluid (pH 7.4) at 37°C. Background levels derived from Mock cells were subtracted, and uptake measurements were normalized to total cell protein and uptake in vehicle treated cells. Each value represents the mean ± SEM from three independent experiments. ***, p< 0.001; **, p<0.005; *, p<0.05, significantly different than substrate uptake in control group. TLCAS, taurolithocholic acid sulfate.