Regulation of Gonadotropin α Subunit Gene Expression by Dopamine D2 Receptor Agonist in Clonal Mouse Gonadotroph αT3-1 Cells1

Kanasaki, Haruhiko; Yonehara, Toshie; Yamada, Yoko; Takahashi, Kentaro; Hata, Kohkichi; Fujiwaki, Rituto; Yamamoto, Hideyuki; Takeuchi, Yukiko; Fukunaga, Kohji; Miyamoto, Eishichi; Miyazaki, Kohji

doi:10.1095/biolreprod67.4.1218

Cited by 17 publications

(11 citation statements)

References 40 publications

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“…The optimal GnRH dose required to generate a maximal mRNA response (i.e. 10 K7 M) was previously determined by dose-response tests at 90 min and 24 h. The doses of Br (a specific dopamine-D 2 receptor agonist) and PRL employed in this study were selected on the basis of their previously observed effectiveness at inducing a biological response in preliminary studies, and in previous work in aT 3 -1 (Kanasaki et al 2002) and primary (Gregory et al 2004) cultures. Following incubation, the medium was aspirated off prior to cell lysis and RNA extraction.…”

Section: Methodsmentioning

confidence: 99%

“…1 mg/ml ethidium bromide and quantified by scanning densitometry using Bio-Rad Quantity One Quantification Software. The amounts of PCR products of each subunit were normalised to those of the PCR products of GAPDH in each sample and the values were converted to a percentage of the control in order to allow a direct comparison between individual experiments (Kanasaki et al 2002).…”

Section: Rt-pcrmentioning

confidence: 99%

“…An immortalised gonadotroph cell line, aT 3 -1, has been shown to express D 2 -type dopamine receptors and it has been suggested that these receptors negatively regulate pituitary a-subunit gene expression in association with a cAMP-dependent pathway (Kanasaki et al 2002), making it possible to investigate the direct effect of dopamine on a gonadotroph monoculture. aT 3 -1 is a mouse-derived cell line which expresses the mouse gonadotrophin a-subunit gene and synthesises and secretes the a-subunit protein (Windle et al 1990).…”

Section: Introductionmentioning

confidence: 99%

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Direct effects of prolactin and dopamine on the gonadotroph response to GnRH

Henderson

Townsend²,

Tortonese³

2008

Journal of Endocrinology

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The intrapituitary mechanisms underlying the inhibitory actions of hyperprolactinaemia on the reproductive axis remain unclear. Previous work on primary pituitary cultures revealed combined suppressive effects of prolactin (PRL) and dopamine on the gonadotrophin response to GnRH. However, whether these effects occur directly at the level of the gonadotroph and are accompanied by changes in gene expression is still unresolved. Here, aT 3 -1 and LbT2 cells were used to investigate the effects of PRL and dopamine on gonadotrophin synthesis and release in gonadotroph monocultures under basal and GnRH-stimulated conditions. PRL receptor and dopamine receptor mRNA expressions were first determined by RT-PCR in both cell lines. Then, PRL and the dopamine agonist bromocriptine (Br), alone or in combination, were shown to block the maximal a-subunit and LHb-subunit mRNA responses to a dose-range of GnRH. The LH secretory response was differentially affected by treatments. GnRH dose-dependently stimulated LH release, with a 4-5 fold increase at 10 K8 M GnRH. Unexpectedly, PRL or Br stimulated basal LH release, with PRL, but not Br, enhancing the LH secretory response to GnRH. This effect was, however, completely blocked by Br. These results reveal direct effects of PRL and dopamine at the level of the gonadotroph cell, and interactions between these two hormones in the regulation of gonadotrophin secretion. Moreover, uncoupling between LH synthesis and release in both the basal and the GnRH-stimulated responses to PRL and dopamine was clearly apparent.

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Section: Methodsmentioning

confidence: 99%

Section: Rt-pcrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Direct effects of prolactin and dopamine on the gonadotroph response to GnRH

Henderson

Townsend²,

Tortonese³

2008

Journal of Endocrinology

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“…Therefore, PRL and DA can act directly at the level of the gonadotroph to evoke their effects. However, whereas the cellular and molecular effects of DA in the gonadotroph are reasonably well defined [11,13], those of PRL are not.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Effects of Prolactin in Gonadotroph Target Cells1

Hodson

Townsend

Tortonese

2010

Biology of Reproduction

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Hyperprolactinemia is a major cause of infertility, brought about by inhibition of gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus and impairment of luteinizing hormone (LH) output from the pituitary gland. However, whereas the actions of prolactin (PRL) within the brain have been investigated extensively, its specific effects at the level of pituitary gonadotroph target cells remain unclear. Here, we provide evidence that the actions of PRL within the gonadotroph are more complex than originally envisaged. Using a gonadotroph cell monoculture, the first series of experiments showed that PRL is, paradoxically, a potent stimulator of LH release, with a three- to fourfold increase in LH values at hyperprolactinemic concentrations of PRL. Conversely, PRL dose-dependently modulated the LH secretory response to GnRH in a biphasic manner, with classical suppression of LH output only detected under a narrow dose range. In contrast, at all doses tested, PRL blocked the LHB mRNA response to the secretagogue. Subsequent studies revealed that the stimulatory effects of PRL on LH release are not mediated by the conventional cytokine receptor pathways but, rather, by a novel JAK2-PIK3-PKC-dependent signaling cascade. Moreover, the experiments showed that these actions of PRL within gonadotroph cells are controlled by dopamine, the main hypothalamic inhibitory regulator of PRL release in vivo. Our findings have unraveled specific actions of PRL within the gonadotroph and the cell-signaling interactions that ultimately underlie hyperprolactinemia-induced infertility.

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“…We proposed one potential negative regulator (dopamine) that might interrupt PACAP expression in gonadotrophs. The dopamine-2 receptor, Drd2, has been demonstrated to be expressed in T3 and L T2 gonadotroph cell lines (Kanasaki et al, 2002;Mutiara et al, 2006). Drd2 couples to G I to inhibit adenyl cyclase activity, and reduce cAMP levels (Missale et al, 1998) whereas PACAP increases the level of cAMP in gonadotroph cells.…”

Section: Dopamine-2 Receptor Activation Decreases Pacap Expression Inmentioning

confidence: 99%

PACAP : a novel neuropeptide for pituitary gonadotroph maturation, function and regulation.

Yang¹

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Regulation of Gonadotropin α Subunit Gene Expression by Dopamine D2 Receptor Agonist in Clonal Mouse Gonadotroph αT3-1 Cells1

Cited by 17 publications

References 40 publications

Direct effects of prolactin and dopamine on the gonadotroph response to GnRH

Direct effects of prolactin and dopamine on the gonadotroph response to GnRH

Characterization of the Effects of Prolactin in Gonadotroph Target Cells1

PACAP : a novel neuropeptide for pituitary gonadotroph maturation, function and regulation.

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