Effect of TNF-, IL-1β, and PMA on the expression of PAI-1 mRNA in UT-7 cell lines. At the initiation of (A) UT-7/OR, (B) UT-7/TPO, (C) UT-7/EPO, and (D) UT-7/EPO-MPL culture, any one of 10 ng/mL TNF-, 10 ng/mL IL-1β, and 10 nmole/mL PMA was added to the culture. The cells were harvested at the indicated times (0, 24, and 48 hours) and examined by RT-PCR followed by Southern blot analysis. Each value (mean ± SD, n = 3) shows the ratio of PAI-1 expression after 24 and 48 hours of culture versus the respective control (0 hour) expression.