Hormone changes during ovulation and effects of steroid hormones on plasma gonadotropin levels and ovulation in goldfish

Kobayashi, Makito; Aida, Katsumi; Hanyu, Isao

doi:10.1016/0016-6480(87)90201-2

Cited by 107 publications

(39 citation statements)

References 27 publications

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“…Furthermore, cAMP levels in both receptortransfected cell lines were significantly decreased in a concentration-and time-dependent manner in response to physiologically relevant concentrations of 17,20b-DHP. Although circulating levels of 17,20b-DHP have not yet been measured in zebrafish due to their small size, MIS concentrations (1-10 nM) that were effective in significantly decreasing cAMP levels and activating MAPK in this experiment are within the range found in the plasma of a variety of fish species during oocyte maturation and ovulation (Kobayashi et al 1987, Truscott et al 1992, King et al 1994. The finding that the MIS, 17,20b-DHP, is the preferred ligand for the zebrafish mPRs is important for establishing their ovarian functions in the presence of a variety of similar progestin derivatives in the ovary.…”

Section: Discussionmentioning

confidence: 75%

Cell-surface expression, progestin binding, and rapid nongenomic signaling of zebrafish membrane progestin receptors α and β in transfected cells

Hanna¹,

Pang²,

Thomas³

et al. 2006

Journal of Endocrinology

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Recently, a unique family of membrane progestin receptors (mPRa, mPRb, and mPRg) was identified, which may be responsible for mediating rapid, nongenomic actions of progestins in a variety of target tissues. In this study, the mPRa and mPRb isoforms from zebrafish were shown to be rapidly and specifically activated by the maturation-inducing steroid (MIS) of this species, . The zebrafish mPRa and a previously uncharacterized mPRb isoform were stably expressed in nuclear progesterone receptor-deficient mammalian breast cancer cells, MDA-MB-231. Expression and surface localization of the receptors were verified by flow cytometry, biotin surface labeling, and Western blotting. Plasma membrane proteins from mPRa-or mPRb-transfected cells showed high affinity (mPRa, K d 7 nM; mPRb, K d 12 nM), saturable, displaceable, single-binding sites specific for 17,20b-DHP, whereas negligible specific 17,20b-DHP binding was observed in nontransfected cells. Progestin treatment caused significant activation of mitogen-activated protein kinase (MAPK) within 5 min in cells transfected with either of the receptors as measured by western blotting and flow cytometry. The rank order of the potencies of several progestins in activating MAPK via mPRa and mPRb was the same (17,20b,. Interestingly, the MIS in zebrafish, 17,20b-DHP, was also the most potent inhibitor, among the progestins tested, of adenylyl cyclase activity in cells transfected with either of the receptors. This progestin significantly decreased cAMP levels in both mPRa-and mPRb-transfected cells in a dose-responsive and timedependent manner. In addition, signaling of the zebrafish mPRa was blocked by pertussis toxin, implying activation of a G i protein, while sensitivity to pertussis or cholera toxin was not shown with mPRb-mediated signaling, possibly indicating that this receptor activates a different pertussis toxin-insensitive G protein. The results of this study suggest that zebrafish mPRa and mPRb signal similarly upon progestin binding resulting in rapid activation of MAPK and downregulation of adenylyl cyclase activity.

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Section: Discussionmentioning

confidence: 75%

Cell-surface expression, progestin binding, and rapid nongenomic signaling of zebrafish membrane progestin receptors α and β in transfected cells

Hanna¹,

Pang²,

Thomas³

et al. 2006

Journal of Endocrinology

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“…Similar to those in mammals (Gharib et al 1990, Burger et al 2004, the secretion and expression of fish gonadotropins are controlled by both neuroendocrine factors from the hypothalamus such as gonadotropin-releasing hormone (GnRH; Peter et al 1986, Weltzien et al 2004, Ando & Urano 2005 and steroids from the gonads (Kobayashi et al 1987, Dickey & Swanson 1998. Our previous study in the goldfish demonstrated that in addition to the neuroendocrine and endocrine regulation, pituitary gonadotropins are also subject to local paracrine regulation by activin (Yam et al 1999a, Yuen & Ge 2004, similar to the situation in mammals (Roberts et al 1989, Corrigan et al 1991, Bilezikjian et al 2004.…”

Section: Introductionmentioning

confidence: 79%

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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“…T ! progestagen is common to most teleosts and is the result of a GtH-mediated shift in steroidogenesis, in which there is a progressive decrease in aromatase activity and concomitant activation of 20b-hydroxysteroid dehydrogenase (20b-HSD) to produce the maturation-inducing steroid (MIS, Kobayashi et al, 1987;Nagahama et al, 1995;Scott et al, 1983). In Lusitanian toadfish 17,20b,21-P, has been identified as the probable MIS by in vitro studies (Modesto and Canario, 2002) and that is supported in the current study by the elevated 17,20b,21-P during spawning and the simultaneous absence of 17,20b-P.…”

Section: Discussionmentioning

confidence: 99%

Morphometric changes and sex steroid levels during the annual reproductive cycle of the Lusitanian toadfish, Halobatrachus didactylus

Modesto

Canário

2003

General and Comparative Endocrinology

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Hormone changes during ovulation and effects of steroid hormones on plasma gonadotropin levels and ovulation in goldfish

Cited by 107 publications

References 27 publications

Cell-surface expression, progestin binding, and rapid nongenomic signaling of zebrafish membrane progestin receptors α and β in transfected cells

Cell-surface expression, progestin binding, and rapid nongenomic signaling of zebrafish membrane progestin receptors α and β in transfected cells

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

Morphometric changes and sex steroid levels during the annual reproductive cycle of the Lusitanian toadfish, Halobatrachus didactylus

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