Testicular autoregulation: possible role for 7-alpha-hydroxylated androgens

GC-MS-based metabolic signatures reveal comparative steroidogenic pathways between fetal and adult mouse testes

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.

Temporal changes in the serum levels of gonadotrophins and testosterone in male rats bearing subcutaneous implants of 5 alpha-dihydrotestosterone

This study has assessed the effect of s.c. implants of 5 alpha-dihydrotestosterone (DHT) on the blood levels of testosterone and gonadotrophins in intact and castrated adult male rats. The rats were bled via cardiac puncture at 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70 days after DHT implantation. On days 28 and 49 post-implantation, rats were injected with LHRH (25 ng) and bled 15 min later. In intact rats bearing DHT implants, the serum levels of LH and testosterone were suppressed significantly with no significant changes in FSH levels. Ventral prostate, seminal vesicles and the pituitary were reduced significantly in weight when compared with controls with empty implants. DHT significantly inhibited LHRH-induced release of FSH in intact rats. In castrated rats, DHT implants inhibited the secretion of both LH and FSH, with a rise in serum DHT levels. DHT stimulated the LHRH-induced release of LH but inhibited FSH. DHT implants increased the weight of the seminal vesicles and ventral prostate but inhibited the weight of the pituitary when compared to castrated rats bearing empty implants. This study demonstrates specific inhibition of serum LH and testosterone by DHT implants in intact adult rats.