Localization of Δ4-5β and 5α-Reductases and 17β-ol-Dehydrogenase in Immature Golden Hamster Testes*

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Abstract
Testes of 28- and 70-day-old golden hamsters were separated into seminiferus tubules and interstitial tissue by wet dissection. Homogenates of the tissues and subcellular fractions were incubated with [14C]androstenedione, and NADPH and enzyme activity (nanomoles per 100 mg protein/h) was estimated. In immature testes, the 5β-reductase activity was largely confined to the seminiferous tubules, while 5α-reductase was localized in the interstitial tissue. The activity of 17β-oldehydrogenase was found to be equally distributed between tubules and interstitial tissue. Although the activities of 5β- and 5α-reductases were approximately 10 times greater in immature than adult testes, the 17β-ol-dehydrogenase activity in adult testes was approximately 10 times that in immature testes. In the immature testes, most 5α-reductase and 17β-ol-dehydrogenase were localized in microsomes, whereas 5β-reductase was wholly localized in cytosol. These results indicate that 5β-reduction of Δ4-3-ketosteroids takes place largely in cytosol of tubular cells, while 5α-reduction occurs in microsomes of interstitial cells in the testis of the immature golden hamster.

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