TPO mRNA expression in IL-6–treated HepG2 cells.

(A) To determine the effect of IL-6 on TPO mRNA levels in vitro, HepG2 cells were cultured with increasing concentrations of huIL-6 for 12 hours, total RNA extracted, gel-electrophoresed, blotted onto nylon membranes, and hybridized with radioactively labeled huTPO and β-actin cDNA. The figure is representative of 3 independent experiments. (B) Nuclear run-off transcription in IL-6–treated HepG2 cells. Nuclei of HepG2 cells cultured with huIL-6 (1 ng/mL) or left untreated were prepared after 24 hours of stimulation. Purification of nuclei and in vitro transcription were performed as described in “Materials and methods.” The left panel shows a representative hybridization. Densitometric evaluation of the respective experiment is presented in the right panel in arbitrary units as counts × mm⁻² [huTPO]/counts × mm⁻²[β-actin].