Testosterone regulation of gonadotropin production in goldfish

Habibi, Hamid R.; Huggard, Danielle

doi:10.1016/s0742-8413(98)00022-x

“…In the goldfish, previous studies using incubated pituitary fragments demonstrated stimulatory effects of testosterone and E 2 on the expression of both FSHb and LHb; however, FSHb appeared to be less responsive to E 2 treatment than LHb (Huggard et al 1996, Habibi & Huggard 1998, Huggard-Nelson et al 2002. The in vitro effect of E 2 on gonadotropin subunit expression, especially that of FSHb, seemed to be dependent on the stage of sexual maturity.…”

Section: Discussionmentioning

confidence: 83%

Evidence for the existence of a local activin–follistatin negative feedback loop in the goldfish pituitary and its regulation by activin and gonadal steroids

Cheng¹,

Yuen²,

Ge³

2007

Journal of Endocrinology

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Activin is an important regulator of gonadotropin expression and production in the vertebrate pituitary, and its activity is fine-tuned by its binding protein follistatin. In the present study, a full-length cDNA for follistatin was cloned in the goldfish, which shows 74% amino acid sequence identity with that of mammals. Recombinant goldfish follistatin expressed in the Chinese hamster ovary cells significantly blocked activin-induced F5-5 cell differentiation. Goldfish follistatin is expressed in a wide range of tissues including the brain, pituitary, ovary, and testis. The expression of follistatin mRNA in the pituitary is regulated by both activin and gonadal steroids in vitro. Treatment with goldfish activin B for 48 h significantly up-regulated follistatin expression in cultured pituitary cells, suggesting a closed activin-follistatin feedback loop in the pituitary. In agreement with this, both human and goldfish follistatin down-regulated the expression of follistatin itself, probably due to the neutralization of endogenous activin. Examination of FSHb and LHb expression in the same samples supports the role of activin and follistatin in the differential regulation of FSH and LH as demonstrated previously. Since the expression level of activin b B in the pituitary is rather stable both in vitro and in vivo, it is conceivable that follistatin may play a pivotal regulatory role in the intra-pituitary activin system. Both estradiol and testosterone up-regulated follistatin expression in vitro, suggesting a mediating role for follistatin in steroid feedback on pituitary hormones. These results provide clues to the potential physiological roles of activin-follistatin system in the regulation of gonadotropin biosynthesis in teleosts.

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“…This implies that MDHT not only inhibits vitellogenesis of oocytes but also inhibits previtellogenic growth. These effects can be explained by direct androgen regulation of oocyte functions, in view of the presence of androgen receptors in the ovary [26], or through feedback at the level of the pituitary [27–29].…”

Section: Discussionmentioning

confidence: 99%

Histopathology as a tool for the evaluation of endocrine disruption in zebrafish (Danio rerio)

Ven¹,

Wester²,

Vos³

2003

Enviro Toxic and Chemistry

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The importance of histology as a tool in the evaluation of endocrine disruption in fish depends on the choice and interpretation of appropriate endpoints, as is illustrated by the analysis of the effects of exposure to the estrogen 17beta-estradiol (E2) and the nonaromatizable androgen 17-methyldihydrotestosterone (MDHT). The E2 led to the disappearance of vitellogenic oocytes in the ovary and an increased area of relatively large, eosinophilic cells in the testis, which were identified as spermatogonia under high-power magnification; this was a relative increase, as was shown by histomorphometry, because of a decreased size of spermatogenic cysts and a relative decrease of spermatocyte cysts. The E2 also induced an accumulation of acidophilic fluid in vessels and interstitial spaces, confirmed by immunohistochemistry as vitellogenin, and basophilia in the liver also associated with the production of vitellogenin. The MDHT induced activation of Sertoli cells in the testis and a decreased presence of vitellogenic oocytes and a reduced growth of previtellogenic oocytes in the ovary. These observations indicate the advantages of examining multiple organ systems on whole-body sections and the application of adequate magnifications. Inclusion of additional techniques such as morphometry and immunohistochemistry is valuable to further uncover insidious effects of endocrine disruptors.

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“…This implies that MDHT not only inhibits vitellogenesis of oocytes but also inhibits previtellogenic growth. These ef-fects can be explained by direct androgen regulation of oocyte functions, in view of the presence of androgen receptors in the ovary [26], or through feedback at the level of the pituitary [27][28][29].…”

Section: Discussionmentioning

confidence: 99%

Histopathology as a Tool for the Evaluation of Endocrine Disruption in Zebrafish (Danio Rerio)

Ven¹,

Wester²,

Vos³

2003

Environ Toxicol Chem

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The importance of histology as a tool in the evaluation of endocrine disruption in fish depends on the choice and interpretation of appropriate endpoints, as is illustrated by the analysis of the effects of exposure to the estrogen 17beta-estradiol (E2) and the nonaromatizable androgen 17-methyldihydrotestosterone (MDHT). The E2 led to the disappearance of vitellogenic oocytes in the ovary and an increased area of relatively large, eosinophilic cells in the testis, which were identified as spermatogonia under high-power magnification; this was a relative increase, as was shown by histomorphometry, because of a decreased size of spermatogenic cysts and a relative decrease of spermatocyte cysts. The E2 also induced an accumulation of acidophilic fluid in vessels and interstitial spaces, confirmed by immunohistochemistry as vitellogenin, and basophilia in the liver also associated with the production of vitellogenin. The MDHT induced activation of Sertoli cells in the testis and a decreased presence of vitellogenic oocytes and a reduced growth of previtellogenic oocytes in the ovary. These observations indicate the advantages of examining multiple organ systems on whole-body sections and the application of adequate magnifications. Inclusion of additional techniques such as morphometry and immunohistochemistry is valuable to further uncover insidious effects of endocrine disruptors.

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Testosterone regulation of gonadotropin production in goldfish

Cited by 13 publications

References 58 publications

Evidence for the existence of a local activin–follistatin negative feedback loop in the goldfish pituitary and its regulation by activin and gonadal steroids

Evidence for the existence of a local activin–follistatin negative feedback loop in the goldfish pituitary and its regulation by activin and gonadal steroids

Histopathology as a tool for the evaluation of endocrine disruption in zebrafish (Danio rerio)

Histopathology as a Tool for the Evaluation of Endocrine Disruption in Zebrafish (Danio Rerio)

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