Thyrotropin releasing hormone stimulates metabolism of phosphatidyl inositol in GH<sub>3</sub> cells

Schlegel, Werner; Roduit, Claude; Zahnd, G

doi:10.1016/0014-5793(81)80547-9

Cited by 39 publications

(8 citation statements)

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“…Moreover, our results are in agreement with the finding of stimulated 32 P incorporation into PI and phosphatidic acid induced by TRH and TRH analogs in PRL-secreting GH 3 pituitary cells. The labeling of other phospholipids was also not affected in this system (25)(26)(27). Bombesin, at concentrations capable of stimulating PRL secretion, exerted a similar effect on PI turnover (27).…”

Section: Discussionmentioning

confidence: 58%

“…In 1958, Hokin et al (21) suggested that phospholipids, in particular PI, play a role in the active secretion of polypeptide hormones by the anterior pituitary gland. Young et al (22) reported that acetylcholine in the presence of physostigmine, a choline esterase inhibitor, increased the release of GH and the efflux of 45 (23,24) and to enhanced PRL secretion induced by TRH (25)(26)(27) or bombesin (27), but not by vasoactive intestinal peptide (27), in GH 3 cells. We investigated the effect of dopamine on PI turnover in anterior pituitary glands both in vitro and in vivo, using the incorporation of radiolabeled phosphate into PI and other phospholipids [phosphatidylcholine (PC) and CANONICO, VALDENEGRO, AND MACLEOD Endo«1983 Volll3«Nol phosphatidylethanolamine (PE)] as an index (19).…”

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confidence: 98%

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The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine^*

et al. 1983

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We studied the association between the inhibition of phosphatidylinositol (PI) turnover and the inhibition of PRL secretion in the presence of dopamine. The incorporation of radiolabeled phosphate into anterior pituitary gland PI as well as serum PRL levels were significantly (P less than 0.01) greater in female than in male rats. No significant sex-related difference was found in the incorporation by pituitary tissue of 32P into phosphatidylcholine (PC) or phosphatidylethanolamine (PE). Dopamine decreased the incorporation of 32P into PI, but not into PC or PE, by female rat pituitary glands; this effect was reversed by two dopamine receptor-blocking agents, haloperidol and pimozide. After dopamine was removed from the incubation medium, basal 32P incorporation into PI was restored within 10 min. The administration of bromocriptine (500 micrograms/kg, ip, 4 h earlier) significantly reduced pituitary PI turnover. Conversely, in vivo injection of alpha-methyl-p-tyrosine (alpha MpT; 200 mg, ip, 2.5 h before death), an inhibitor of catecholamine biosynthesis, dramatically increased serum PRL levels. In vitro incorporation of 32P into PI, but not into PC or PE, increased (+130%) when these glands were incubated for 30 min with radiolabeled phosphate. The in vitro addition of 0.5 microM dopamine to glands from alpha MpT-treated rats counteracted the stimulation of 32P incorporation into PI produced by alph MpT treatment. In rats bearing the transplantable PRL-secreting tumor MtTW15, the hyperprolactinemia produced by the tumor stimulates hypothalamic turnover of dopamine, with a consequent inhibition of pituitary gland PRL secretion. 32P incorporation into PI, but not into PC or PE, was significantly (P less than 0.01) inhibited (-41%) in pituitary glands from these rats. The injection of alpha MpT (200 mg/kg, ip) or haloperidol (2 mg/kg, ip) 12 and 3 h before death into MtTW15 tumor-bearing rats abolished the inhibition of 32P incorporation into pituitary PI. Dopamine also decreased PI turnover in the 7315a PRL-secreting pituitary tumor. Our data indicate that the PI cycle may be an intracellular mechanism controlling PRL release in the rat and that the changes in its cleavage and turnover may be an early postreceptor event responsible for the inhibition of PRL secretion produced by factors such as dopamine.

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Section: Discussionmentioning

confidence: 58%

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confidence: 98%

The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine^*

et al. 1983

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“…1, induction of c-fos mRNA by TRH was dose-dependent over a range similar to that observed for TRH stimulation of phospholipase C (e.g. Schlegel et al 1981), Ca + mobilization (Albert & Tashjian, 1984) and prolactin secretion (Dannies & Tashjian, 1973 (Schlegel & Wollheim, 1984). The cells were then stimulated in the same medium, thereby inhibiting Ca + influx and store replenishment.…”

Section: Physiological Doses Of Trh Increase C-fosmentioning

confidence: 90%

Induction of c-fos in pituitary cells by thyrotrophin-releasing hormone and phorbol 12-myristate 13-acetate depends upon Ca2+ influx

Godson

Roche

et al. 1994

Journal of Molecular Endocrinology

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The role of cytosolic free Ca2+ ([Ca2+]i) in the induction of the immediate early gene c-fos by TRH or by phorbol 12-myristate 13-acetate (PMA) was studied in the clonal pituitary cell line GH4C1. It was found that c-fos mRNA levels were rapidly and transiently increased by TRH at physiological concentrations (1-100 nM). The effect of TRH was dependent on a rise in [Ca2+]i, and TRH stimulation of Ca2+ influx was essential for c-fos induction. Cell depolarization with K+, which produces a [Ca2+]i rise by soliciting Ca2+ influx via voltage-gated Ca2+ channels, was insufficient to induce c-fos. Blockade or downregulation of protein kinase C (PKC) strongly attenuated TRH stimulation of c-fos expression. Direct stimulation of PKC by PMA raised c-fos mRNA levels, but only under conditions permitting Ca2+ influx. We conclude that TRH induces c-fos mRNA by a mechanism dependent on PKC activation and on Ca2+ influx. The essential role of Ca2+ influx for PMA stimulation of c-fos mRNA suggests a novel pathway linking PKC stimulation to early gene expression.

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“…The studies I emphasize have been performed in cells prelabeled with precursors to isotopic equilibrium in order to facilitate measurement of changes in the cellular content of even minor substances, such as PtdIns(4, 5)P2 and InsP3. Hence, the earlier studies in which the polyphosphoinositides, P tdlns(4,5)P 2 and phosphatidyl inositol 4-phosphate (Ptdlns4P), were measured in cells labeled briefly with [ 3 2p]phosphate will not be described (15,54,57,64).The effects of TRH on phosphoinositides and on inositol sugars have been determined in cells labeled to isotopic steady state with [ 3 H]inositol (5-7, 14, 15,39,44,45,52,53,58). The findings reported in most of these studies are very similar.…”

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Mechanism of Thyrotropin Releasing Hormone Stimulation of Pituitary Hormone Secretion

Gershengorn¹

1986

Annu. Rev. Physiol.

311

120

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INTRODUCTIONDuring the past several years, the mechanism of action of thyrotropin-releasing hormone (TRH; thyroliberin) has been studied intensively in GH cells, cloned rat mammotropic tumor cell lines that appear to be valid models for in vitro study of mammotroph fu nction (30,34,48). In this article I review the recent findings (see 26 for previous review) that fo rm the basis for a detailed hypoth esis to explain the transduction of the TRH signal at the cell surface into stimulation of prolactin secretion.It is generally agreed that an elevation of cyt9plasmic free calcium ion concentration ([Ca2+]i) serves to couple, at least in part, the binding of many hormones and neurotransmitters to plasma membrane receptors with the stimulation of a variety of cellular processes (51). The elevation of [ Ca2+]i induced by these stimulants may be caused by mobilization (or redistribution) of intracellular calcium, or by enhancement of influx of extracellular Ca2+ , or both (17). It has been demonstrated that in some of these cells a very rapid effect after stimulant-receptor interaction is enhanced hydrolysis of phosphatidylin ositoI4,5-bisphosphate [PtdIns( 4,5)P 2 ] by a phospholipase C (or phosphodies terase) to yield 1 ,2 -diacylglycerol (DG) and inositoltrisphosphate (InsP3) (18). Furthermore, it has been proposed that both DG (50) and InsP3 (11) may serve as intracellular mediators (or second messengers) to transduce and amplify the signal, leading to stimulation of the physiologic response(s). DG appears to 515 0066-4278/86/0315-0515$02.00Annu. Rev. Physiol. 1986.48:515-526. Downloaded from www.annualreviews.org Access provided by University of California -Davis on 02/04/15. For personal use only. Quick links to online content Further ANNUAL REVIEWS 516 GERSHENGORN exert its effects by enhancing the activity of a Ca 2 + -and phospholipid dependent protein kinase (protein kinase C) by an action that does not depend on an elevation of [Ca2+];. InsP3 appears to act to mobilize calcium from an intracellular pool to elevate [Ca2+]i' In addition, influx of extracellular calcium may be enhanced by hormones and neurotransmitters to elevate [Ca2+]i' The elevation of [Ca2+]; may activate a Ca2+ -and calmodulin-dependent protein kinase(s) and, perhaps, other processes. It appears that this generalized schema of signal transduction by separate but converging pathways involving Ca2+ �nd lipid messengers may describe the mechanism of TRH stimulation of prolactin secretion. TRH AND PHOSPHOINOSITIDESIn this section I present evidence that strongly supports the concept that in GH cells TRH acts to stimulate the hydrolysis of Ptdlns(4,5)P 2 by a phospholipase C to yield InsP 3 and DG, and that this action may be the initial step in the sequence of intracellular events leading to prolactin secretion. The studies I emphasize have been performed in cells prelabeled with precursors to isotopic equilibrium in order to facilitate measurement of changes in the cellular content of even minor substances, such as PtdIns(4, 5)P2 and InsP3. ...

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Thyrotropin releasing hormone stimulates metabolism of phosphatidyl inositol in GH₃ cells

Cited by 39 publications

References 8 publications

The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine^*

The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine^*

Induction of c-fos in pituitary cells by thyrotrophin-releasing hormone and phorbol 12-myristate 13-acetate depends upon Ca2+ influx

Mechanism of Thyrotropin Releasing Hormone Stimulation of Pituitary Hormone Secretion

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Thyrotropin releasing hormone stimulates metabolism of phosphatidyl inositol in GH3 cells

Cited by 39 publications

References 8 publications

The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine*

The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine*

Induction of c-fos in pituitary cells by thyrotrophin-releasing hormone and phorbol 12-myristate 13-acetate depends upon Ca2+ influx

Mechanism of Thyrotropin Releasing Hormone Stimulation of Pituitary Hormone Secretion

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Thyrotropin releasing hormone stimulates metabolism of phosphatidyl inositol in GH₃ cells

The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine^*

The Inhibition of Phosphatidylinositol Turnover: A Possible Postreceptor Mechanism for the Prolactin Secretion-Inhibiting Effect of Dopamine^*