Long-term induction of transgenic hepcidin. (A) Liver hepcidin mRNA levels. Control mice and inducible mice (ie, double transgenic mice harboring both tetO-Hepc1 and rTA^LAP-1 transgenes) were given doxycycline in their drinking water for 3 weeks. Total liver RNA (20 μg) was fractionated by electrophoresis, blotted, and hybridized with hepcidin and 18S-labeled probes. Values for RBC count, hemoglobin (HGB) level, and serum iron level are shown for each animal. Thepc indicates transgenic hepcidin mRNA; endo hepc, endogenous hepcidin mRNA. (B) Hematologic indices of mice treated for 10, 14, or 20 days with doxycycline. Results are expressed relative to control serum parameters (arbitrarily 100 ± standard deviation). Control animals, □; inducible mice, ▪. Statistical analysis was performed using Student t test (unpaired, 2 tailed): ^*P < .05, n = at least 5 animals. RBC indicates red blood cell count (10⁶/μL); HGB, hemoglobin (g/dL); HCT, hematocrit (%); MCV, mean cell volume (fl).