Figure 2.

Uptake of [³H]thiamine by TRMA fibroblasts. (a) Time course of uptake. Cells were washed and placed in thi– medium 1 day before assay. Uptake was measured for times shown, at 37°C, in serum-free medium supplemented with 66nM thiamine as described in Methods (mutant, –/–; heterozygote, +/–; normal, +/+). Means of duplicate wells are given. Values are corrected for cell-associated radioactivity at 0°C. (b) Defective specific uptake in TRMA^–/– cells, assessed after 30 min incubation at 37°C. Specific uptake was calculated by subtracting radioactivity incorporated in the presence of 3 mM unlabeled thiamine. Means of duplicate wells from one subject of each genotype are represented. Error bars represent ranges for duplicate determinations.