PlGF and ET-1 augment cytochemokine mRNA expression. THP-1 (10⁶ cells/mL) were either treated with PlGF for 24 hours (250 ng/mL) or ET-1 (250 nmol/L) for 30 minutes. For priming, THP-1 cells were first treated with PlGF for 24 hours, washed with PBS and then treated with ET-1 for 30 minutes. Total mRNA was isolated and RPA was performed as described under “RNase protection assay.” The data are representative of 3 independent experiments. Where indicated, the vertical lines show the repositioned gel lanes.