FIGURE 1.

Rapid internalization of Aβ by TR-BBB cells. A, TR-BBB cells were incubated with ¹²⁵I-Aβ at 37 °C (filled squares) or 4 °C (open squares) for 0, 3, 5, and 10 min, and the amount of ¹²⁵I-Aβ uptake was quantitated as cell/medium ratio. The mean ± S.E. in three independent assays is shown. **, p < 0.001. B, the uptake assay of ¹²⁵I-Aβ was performed in the presence of 0, 30, 100, 300, 1000, and 3000 nm unlabeled Aβ as a competitor. The mean ± S.E. in three independent assays is shown. C, a schematic diagram depicting the uptake assays using Pronase treatment in TR-BBB cells. “Cell-bound Aβ” was defined as radioactivities released by this treatment and “internalized Aβ”as radioactivities associated with cell pellet after the treatment. D, the levels of cell-bound and internalized Aβ were measured in the presence or absence of 3 μm unlabeled Aβ-(1–40) or 3 μm unlabeled Aβ-(1–42), respectively. The mean ± S.E. in three independent assays is shown. **, p < 0.01.