Background: Previous studies on gonadal steroidogenesis have not compared metabolic pathways between fetal and adult mouse testes to date. Objectives: To evaluate comparative metabolic signatures of testicular steroids between fetus and adult mice using gas chromatography-mass spectrometry (GC-MS)-based steroid profiling. Materials and methods: GC-MS with molecular-specific scan modes was optimized for selective and sensitive detection of 23 androgens, 7 estrogens, 14 progestogens, and 13 corticoids from mouse testes with a quantification limit of 0.1-5.0 ng/mL and reproducibility (coefficient of variation: 0.3%-19.9%). Based on 26 steroids quantitatively detected in testes, comparative steroid signatures were analyzed for mouse testes of 8 fetuses on embryonic day 16.5 and 8 adults on postnatal days 56-60. Results: In contrast to large amounts of steroids in adult testes (P <.0002), all testicular levels per weight unit of protein were significantly increased in fetal testes (P <.002, except 6β-hydroxytestosterone of P =.065). Both 11β-hydroxyandrostenedione and 7α-hydroxytestosterone were only measurable in fetal testes, and metabolic ratios of testosterone to androstenediol and androstenedione were also increased in fetal testes (P <.05 for both). Discussion and conclusion: Testicular steroid signatures showed that both steroidogenic Δ4 and Δ5 pathways in the production of testosterone were activated more during prenatal development. Both 7α- and 11β-hydroxylations were predominant, while hydroxylations at C-6, C-15, and C-16 of testosterone and androstenedione were decreased in the fetus. The present GC-MS-based steroid profiling may facilitate understanding of the development of testicular steroidogenesis.
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