Induction of wt-Epo-GFP transgene expression by bleeding anemia in the liver. Anti-GFP immunohistochemistry of the livers from wt-Epo-GFP transgenic mice (line WA) under normal (A, Hct: .45 [45%]) and anemic (B, Hct: .30 [30%]; C, Hct: .15 [15%]) conditions is shown. At the lowest Hct (C), GFP-positive cell regions (brown) had expanded around the central vein (*), but hepatocytes surrounding the interlobular triad (sharp) did not express GFP. (D) Relative Epo mRNA levels in the kidneys and livers from line WA mice under normal (n, ) and anemic (a, ) conditions were measured by quantitative RT-PCR and normalized to the levels of GAPDH mRNA. Hepatocytes surrounding the interlobular triad (IL) and central vein (CV) under anemic conditions were collected using laser microdissection and the expression of Epo mRNA was examined by quantitative RT-PCR. Data are the means (± SD) of 3 independent mice. (E) GFP expression was also detected in E13.5 fetal liver from a wt-Epo-GFP transgenic embryo (line WA). The GFP-positive cells were fetal hepatocytes that were also positive for α-fetoprotein (AFP; red immunofluorescence in panel F). Panels E and F were merged in panel G. Scale bars are 300 μm (A-C) and 20 μm (E-G).