Expression of the type 1 and 2 steroid 5 alpha-reductases in human fetal tissues.

Androgens play a key role in human fetal development. Therefore, it is important to understand the distribution of the isozymes of 5 alpha-reductase, the enzyme that converts testosterone to the more potent androgen, dihydrotestosterone. The expression of the two isozymes of 5 alpha-reductase was studied in human fetal skin and fetal prostate by measuring the in vitro enzyme activity in crude preparations. Low levels of the type 1 5 alpha-reductase were found in fetal scalp and back skin. Studies with fetal prostate samples confirmed that the type 2 enzyme is expressed in levels similar to those found in adult tissues. These results provide the first evidence that both isozymes of 5 alpha-reductase are expressed during human fetal development.