Upregulation of EDN expression during eosinophilic differentiation of HL60 cells. HL60 7.7 cells were treated with BA (0.5 mmol/L) for 1, 2, 4, or 6 days, after which RNA was isolated and analyzed by Northern blotting. Hybridization of the blot with a probe specific for EDN shows that EDN mRNA expression is strongly induced by BA. Reprobing of the blot with a GAPDH probe shows that equal amounts of RNA were loaded in each lane. Scanning of the autoradiograph shows the following increase in EDN expression (relative to GAPDH) compared with wild-type HL60 cells: 2-, 5-, 45-, 160-, and 130-fold increase for 7.7 cells treated for 0, 1, 2, 4, and 6 days, respectively.