Fig. 1. CD induces PAI-1 expression in growth-arrested R22 cells as a function of concentration and time of exposure. CD (in final concentrations of 2, 5 or 10 µM) or DMSO vehicle alone (0 µM) was added to serum-deprived R22 cell cultures. Total RNA was isolated 4 hours later and northern blots hybridized with 32P-labeled PAI-1 and A50 cDNAs (A). PAI-1 mRNA levels increased as a function of CD concentration; maximal expression was attained with 10 µM CD (Hawks and Higgins, 1998). The histogram in (B) represents a quantitative analysis of PAI-1 mRNA abundance (mean±s.d.) from three different experiments normalized to the A50 signal. Immunoblot detection of PAI-1 protein on transfers of electrophoretic separations of R22 cell extracts (20 µg protein/lane) at various times after CD treatment (C). PAI-1 increased as early as 1 hour post-stimulation and reached maximal levels by approximately 4 hours.