Fig. 2. In situ distribution of CD-induced PAI-1 protein in quiescent R22 cells. The fractions of PAI-1 protein-expressing cells and the relative intensity of immunoreactive PAI-1 staining were assessed by fluorescence microscopy; both increased as a function of the time of CD exposure. Nuclei were visualized by DAPI staining. Although microfilament structure was progressively disrupted in 0.1 and 1.0 µM CD-treated cells, PAI-1 expression was only evident in 10 µM CD-stimulated cultures. Induction was more closely associated with changes in cell shape (Fig. 3) than actin skeleton disorganization. The apparent nuclear region accumulation of PAI-1 is probably the collective result of CD-induced cellular arborization and Golgi collapse around the nucleus.