Dynamic Actions of Arachidonic Acid and Protein Kinase C in Pituitary Stimulation by Gonadotropin Releasing Hormone

Chang, John P.; Graeter, Janelle S.; Catt, Kevin J.

doi:10.1210/endo-120-5-1837

Cited by 46 publications

(16 citation statements)

References 20 publications

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“…Cell Column Peri/usion A perifusion system adapted from those used previously by Chang et al [4,7] was used. Dispersed goldfish pituitary cells were resuspend ed in culture medium and incubated overnight at 27 °C under 5% CO; and saturated humidity conditions with preswollen Cytodex-I beads (Pharmacia; 2xl06 cells with 2Ü0 pi beads in 6 ml m edia/60 mm petri dish/column).…”

Section: Sialic Culturementioning

confidence: 99%

Differential Actions of Dopamine Receptor Subtypes on Gonadotropin and Growth Hormone Release in vitro in Goldfish

Chang

Yu²,

Wong³

et al. 1990

Neuroendocrinology

129

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Incubation of cultured goldfish pituitary cells with 10 nM to 1 µM apomorphine (APO), a non-selective dopamine agonist, increased growth hormone (GH) release in a dose-dependent manner. GH release was also stimulated in a dose-dependent manner by 0.1 nM to 1 µM salmon gonadotropin (GTH)-releasing hormone (sGnRH), sGnRH analog, and chicken GnRH-II (cGnRH-II). The magnitude of GH responses to 1 µM GnRHs were less than that to 1 µM APO. GH responses to 10 nM to 1 µM APO were not significantly increased by the addition of GnRHs. Static incubations with 0.1 nM to 1 µM of the dopamine Dl agonist SKF38393 did not alter basal GTH release, or the GTH responses to 10 nM sGnRH and cGnRH-II. In contrast, the Dl agonist SKF38393 significantly increased basal GH secretion with maximal stimulation achieved at 100 nM concentration, and GH responses to 10 nM sGnRH and 10 nM cGnRH-II were enhanced by simultaneous applications of SKF38393. Incubation with 1 µM of the D2 agonist LY171555 decreased basal GTH release. Additions of 0.1 nM to 1 µM LY171555 caused dose-dependent decreases in the GTH secretion induced by 10 nM sGnRH and cGnRH-II. In contrast, basal and GnRH-stimulated GH release were not affected by coincubations with LY171555. The Dl antagonist SKF83566 and the D2 antagonist domperidone, at 1 µM concentrations, specifically blocked the Dl agonist SKF38393-stimulated increase in GH release and the D2 agonist LY171555-induced depression of GTH secretion, respectively. In cell column perifusion studies, the Dl agonist SKF38393 at 0.1 nM to 1 µM had no effects on GTH release, but significantly elevated GH secretion rates when applied at 0.1–1 µM concentrations. The GH release induced by 1 µM SKF38393 was significantly reduced by simultaneous perifusion with 1 µM of the Dl antagonist SKF83566. Treatments with SKF38393 and/or SKF83566 did not affect net GTH and GH responses to sGnRH challenges. In contrast, perifusion with 0.1 and 1 µM of the D2 agonist LY171555 depressed basal as well as sGnRH-induced GTH responses. These effects of 1 µM LY171555 were completely blocked by simultaneous applications of 1 µM domperidone, a D2 antagonist. Treatments with these D2 selective drugs did not affect basal and sGnRH-stimulated GH release. These results indicate that in cultured goldfish pituitary cells, activation of dopamine Dl- and D2-like receptors specifically stimulates GH release and inhibits both basal and stimulated GTH secretion, respectively. The presence of direct actions of sGnRH and cGnRH-II on goldfish GTH an GH release are also demonstrated. This is the first study do demonstrate stimulatory dopamine Dl actions in the vertebrate pituitary.

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Section: Sialic Culturementioning

confidence: 99%

Differential Actions of Dopamine Receptor Subtypes on Gonadotropin and Growth Hormone Release in vitro in Goldfish

Chang

Yu²,

Wong³

et al. 1990

Neuroendocrinology

129

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“…The results have often been contradictory, suggesting a role in GnRH signal transduction for cAMP (3,4), cGMP (5), calcium and 1,2-diacylglycerols (6)(7)(8), and arachidonic acid (9,10). More recently, it has been demonstrated that a crucial event of GnRH action in gonadotrope cells is the stimulation of phosphoinositide turnover leading to diacylglycerol accumulation and raised intracellular free calcium levels (11,12).…”

Section: Introductionmentioning

confidence: 99%

Intracellular Responses to Gonadotropin-Releasing Hormone in a Clonal Cell Line of the Gonadotrope Lineage

Horn¹,

Bilezikjian²,

Perrin³

et al. 1991

Molecular Endocrinology

137

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We recently derived a GnRH-responsive pituitary cell line of the gonadotrope lineage (alpha T3-1) by targeted oncogenesis in transgenic mice. Here, we report studies characterizing the GnRH receptors present in these cells and the intracellular responses to GnRH treatment. The receptors in alpha T3-1 cells show specificity for different GnRH analogs, with dissociation constants very similar to those found in normal rat and mouse pituitary. The concentration of receptors is within the range found in normal pituitary. The addition of GnRH or GnRH agonists increases phosphoinositide turnover and protein kinase-C translocation to membranes, and enhances activation of voltage-sensitive calcium channels. However, GnRH does not affect cAMP levels. Analysis of alpha-subunit mRNA levels demonstrated induction by GnRH and phorbol esters. Our results indicate that GnRH initiates a cascade of intracellular events that generate a set of second messengers, one or more of which is involved in the regulation of gene expression. The responses of alpha T3-1 cells to GnRH appear to have characteristics equivalent to those of primary pituitary gonadotropes, indicating the utility of this cell line as a model system for the study of GnRH responses.

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“…The role of eicosanoids in stimulus-secretion coupling in the anterior pituitary is one of the best characterized systems. Lipoxygenase and epoxygenase products have been implicated in the mediation of hormone-induced release of the pituitary hormones adrenocorticotropin hormone [1,40,43], ~-endorphin [3,45], prolactin [8,29,43], luteinizing hormone [15,16,28,43], and growth hormone [12,13,27,43,58]. The first direct demonstration that eicosanoids may regulate secretion through modulation of electrical activity came from work with identified neurons of the marine snail, Aplysia.…”

Section: Introductionmentioning

confidence: 99%

Constant turnover of arachidonic acid and inhibition of a potassium current inAplysia giant neurons

Carlson

Levitan

1990

J. Membrain Biol.

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Steady-state currents at hyperpolarized membrane potentials were studied in the homologous giant neurons, LP1 and R2, of Aplysia using two-electrode voltage clamp. Nearly half of the steady-state current at voltages more hyperpolarized than -70 mV had characteristics similar to the inwardly rectifying potassium current (IR) described previously in Aplysia neurons. The pharmacological agents 4-bromophenacylbromide, indomethacin, and the phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate were found to modulate IR. IR was stimulated with BPB and indomethacin and inhibited with TPA. These agents altered IR by a mechanism independent of cAMP, which can also modulate IR. The effects of these modulators are consistent with their actions on arachidonic acid (AA) metabolism in Aplysia nervous system, suggesting AA may constitutively inhibit IR. When ganglia were perfused for 12 hr with medium containing BSA to absorb extracellular fatty acids, IR was increased nearly twofold. This increase was partially inhibited by addition of AA to the perfusion medium, and completely inhibited by pretreatment of ganglia with BPB. Although no direct effect of short-term exposure to exogenous AA was observed, long term exposure to exogenous AA and several other unsaturated fatty acids was accompanied by a decrease in IR.

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Dynamic Actions of Arachidonic Acid and Protein Kinase C in Pituitary Stimulation by Gonadotropin Releasing Hormone

Cited by 46 publications

References 20 publications

Differential Actions of Dopamine Receptor Subtypes on Gonadotropin and Growth Hormone Release in vitro in Goldfish

Differential Actions of Dopamine Receptor Subtypes on Gonadotropin and Growth Hormone Release in vitro in Goldfish

Intracellular Responses to Gonadotropin-Releasing Hormone in a Clonal Cell Line of the Gonadotrope Lineage

Constant turnover of arachidonic acid and inhibition of a potassium current inAplysia giant neurons

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