Decreased Erythroid Colony-Forming Cell Response of XTfm/Y Mice to Testosterone and 5β-Dihydrotestosterone*

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Abstract
Although certain tissues of XTfm/Y mice are known to be deficient in androgen-binding sites, the defect has not been documented for bone marrow. To study the bone marrow response to testosterone and its metabolites, we compared the responses of the erythroid colony-forming cell (CFUE) in these mice and their wild counter-parts, XTa/Y mice, using an in vitro methyl cellulose system in the presence of erythropoietin. Testosterone or 5β-dihydrotestosterone (5β-DHT) treatment (5 mg/kg) of Ta/Y mice in vivo before femoral bone marrow culture resulted in a significant increase in CFU-E colonies. However, similar in vivo treatment of Tfm/Y mice with testosterone or 5β-DHT had no effect on CFU-E colony formation. 5α-DHT had no significant effect on Ta/Y or Tfm/Y mouse bone marrow. Testosterone or 5β-DHT added directly to Ta/Y marrow cultures caused an enhancement of CFU-E colony numbers compared with erythropoietin alone. 5α-DHT inhibited colony formation at high concentrations. Testosterone had no effect on Tfm/Y erythroid colonies, whereas 5β-DHT and 5α- DHT significantly inhibited colony formation. These results indicate that Tfm/Y erythroid bone marrow colonies may have an altered response to testosterone and its metabolites compared to that of Ta/Y erythroid colonies. We postulate that the pattern of androgen receptors in the erythroid progenitor cell compartment of Tfm/Y mice is different from that of Ta/Y mice.