Altered adult erythropoiesis in TRα^−/− mice. (A) Hematocrit level of 10-week-old TRα^+/+ (n = 32), TRβ^−/− (n = 28), and TRα^−/− (n = 38) mice. (B) Spleen weight of TRα^+/+ (+/+), TRα^−/− (−/−), and TRα^−/− “poor responder” (−/−*) mice 3 days after phenylhydrazine treatment (n = 6). Spleen weights before treatment were 100 to 120 mg. (C) Hematocrit level of mice taken 3 days after phenylhydrazine treatment (n = 6). (D) Enumeration of hemoglobin-positive (Hb⁺, arrow) and proerythroblasts (blast, arrowhead) in the spleens of phenylhydrazine-treated mice (n = 3). (E) Percentage of circulating reticulocytes (arrow) and erythrocytes (arrowhead) from mice 3 days after phenylhydrazine treatment (n = 3). (F) Total erythroid progenitors (BFU-Es and CFU-Es) in the spleens of TRα^+/+ (+/+) and TRα^−/− (−/−) mice 3 days after phenylhydrazine treatment (n = 3). (G) Morphology of erythroblasts from TRα^+/+ (+/+) and TRα^−/− (−/−) cultured for 3 days ex vivo (n = 3). (H) Flow cytometric analysis of spleen cells from TRα^+/+ (+/+) and TRα^−/−“poor responders” (−/−*) stained with CD71 and Ter119 (n = 4). Means (± SD) are shown. Statistically significant (2-way ANOVA) differences are indicated (*P ≤ .05; **P ≤ .01).