The bioactive and potent androgen 5α-dihydrotestosterone (DHT) has been postulated to be involved in the development of branching morphogenesis in the human fetal lung, but its expression has not been examined. We therefore examined the expression of the androgen receptor (AR) and 5α-reductases (type 1 and type 2), which catalyse the conversion of testosterone into DHT, in the human fetal lung using immunohistochemistry and reverse transcription–PCR (RT-PCR). Immunoreactive AR was detected predominantly in the nuclei of epithelial cells of the budding component of the early gestational fetal lung. 5α-Reductase type 1 immunoreactivity was detected in the cytoplasm of epithelial cells, whereas immunoreactivity for 5α-reductase type 2 was not detected in the samples of human fetal lung examined. RT-PCR also confirmed the presence of AR and 5α-reductase in all fetal lung and epithelial cell lines. The results of our present study suggest that DHT may play an important role in epithelial cells, which might include precursor cells, in which both AR and 5α-reductases are expressed during branching morphogenesis of the human fetal lung.

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