Effect of mild acid wash on TF/VIIa functional activity on polarized Caco-2 cells. Caco-2 cells in transwells were treated for 3 minutes with a mild acid wash (0.1 mol/L glycine, pH 3.0) or with buffer B (control). Cells were washed 3 times with buffer B after the acid treatment and then assayed for TF/VIIa activity as described in the legend to Fig 1. (Note: Polarized cell layers were tested for their integrity after the assay by measuring TER and flow of iodine labeled tracer across the cell layer. There was no loss of integrity after the mild acid wash.) Data are the mean ± SD of 3 independent experiments each in duplicates. Rate of Xa generation measured on the apical surface was taken as 100%.