Enzymes of androgen biosynthesis in the desert mouse Gerbillus dasyurus.

Abstract Enzymatic reactions involved in androgen biosynthesis in Gerbillus dasyurus were investigated in vitro using testicular homogenates. The activity of 20α-hydroxysteroid oxidoreductase was significantly high, but that of the 17,20-lyase and 17β-hydroxysteroid oxidoreductase appeared relatively low. Double label experiments where [ 3 H]5-ene 3β-hydroxysteroids and [ 14 C]4-en-3-oxosteroids were incubated simultancously as substrates, indicated that testosterone is preferentially synthesized via the 4-ene route. The activity of 17β-hydroxysteroid oxidoreductase observed in testes of Gerbillus was the lowest of all the rodents compared. The activity of this enzyme decreased after laboratory rodents were acclimatized to an elevated ambient temperature (35°C, 30–50% relative humidity). The relevance of the enhanced activity of 20α-hydroxysteroid oxidoreductase associated with the low biosynthetic rate of testosterone in desert rodents is discussed.