Erythroid cell proliferation measured by ⁵⁹Fe uptake assay.

Treated β-thalassemic mice (continuous lines), untreated β-thalassemic controls (n = 3, dotted lines), and heterozygous controls (n = 3, dashed lines) were injected with 0.028 MBq (0.75 μCi) of ⁵⁹Fe in the tail vein. (A) Radioactivity in spleen sections (β-imager exposure, 755 minutes). Values are the mean ± SEM of counted cpm/mm² on 8 sections (treated mice), 29 sections (untreated controls), and 38 sections (heterozygote controls). Values scored in mice Nos. 4 and 7 were 551 ± 56 and 711 ± 67, respectively (not shown). Gradation color indicates local radioactivity, according to the scale. (B) Kinetics of the disappearance of radioactivity in plasma. Values correspond to individually treated mice, indicated by number, or are the mean ± SEM for controls.