Panel A and B. HCMEC/D3 cells (Panel A) and HUVECs (Panel B) cultured for 6–7 days in 25 mM glucose were incubated without any additions (Control) or with additions as follows: ascorbate, 125 μM; Tempol, 300 μM; Trolox, 300 μM; N-acetyl cysteine (NAC), 600 μM; or dithiothreitol (DTT), 300 μM. After 60 min, radioactive inulin was added and the transfer assay was carried out. Results are from 6 experiments, with *p < 0.05 compared to 25 mM glucose control.