TPO mRNA expression and TPO plasma levels in IL-6–treated mice.

(A) To evaluate the in vivo effect of IL-6 on TPO mRNA, mice were treated with 4 doses of 1 μg mIL-6 (IL-6) or PBS–0.5% BSA (Control) at 12-hour intervals. Twelve hours after the last dose, messenger RNA was prepared from the liver, gel-electrophoresed, blotted onto nylon membranes, and hybridized with radioactively labeled mTPO and β-actin cDNA. The figure is representative of 3 independent experiments. (B) Plasma TPO in IL-6–treated mice. Mice were treated with 1 μg mIL-6 (▴) or PBS–0.5% BSA (■) at 12-hour intervals for 6 consecutive days. Venous blood was drawn, and plasma was analyzed for mTPO synthesis by specific ELISA. Data are presented as percentage change compared to baseline (control group, 734 ± 90 pg/mL; IL-6 group, 571 ± 77 pg/mL) for n = 6 per group. *P < .05 compared to baseline.