PAI-1 expression and secretion after irradiation. 45 h after irradiation with 2, 5 and 10 Gy, PAI-1 concentrations in the cell lysates (A and B) and cell culture supernatants (C and D) of BHY and FaDu cells were determined by ELISA. Unirradiated cells (0 Gy) served as a control. Mean values ± S.E.M. of three independent experiments, each analyzed in duplicate, are shown relative to the 0 Gy mean value. Associated significance of the irradiated samples vs. the unirradiated control (0 Gy) is indicated (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001).