THE PRESENCE OF BIOSYNTHETIC PRECURSORS AND HETEROGENEOUS MESSENGER RNAs FOR PROLACTIN IN CULTURED RAT PITUITARY TUMOUR CELLS

ABSTRACT 1,25-Dihydroxyvitamin D3(1,25-(OH)2D3) selectively enhances prolactin gene expression in GH4C1 clonal rat pituitary tumour cells. Because this effect requires extracellular Ca2+, we studied the effect of 1,25-(OH)2D3 on another Ca2+-dependent process, agonist-induced hormone secretion. Pretreatment with 1,25-(OH)2D3 (1 nmol/l) caused at least 25-fold sensitization of GH4C1 cells to the voltage-sensitive Ca2+ channel agonist BAY K 8644 (methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5-carboxylate) as a prolactin secretagogue. This inductive effect of 1,25-(OH)2D3 followed a similar time-course to the enhancement of prolactin production. 1,25-(OH)2D3 had no effect on basal or BAY K 8644-induced 45Ca2+ uptake. The Ca2+-selective divalent cation ionophore 11,19,21-trihydroxy-4,6,8,12,14,18,20-heptamethyl-9-oxo-22-(tetrahydro-5 methyl-5-tetra hydro-5-(1-hydroxyethyl)-5-methyl-2-furanyl)-10,16-docosadienoic acid (ionomycin; 12 nmol/l–1·2 μmol/l) caused no significant increase in prolactin secretion in the absence of 1,25-(OH)2D3, but in cells treated with 1,25-(OH)2D3-(1 nmol/l), it increased prolactin secretion by 73% at 12 nmol/l and by a maximum of 98% at 0·12 μmol/l. These data demonstrate that vitamin D markedly enhances the responsiveness of GH4C1 functional pituitary tumour cells to two secretagogues which acts primarily through Ca2+-dependent mechanisms. They support the proposal that 1,25-(OH)2D3 acts in this cultured cell model either by effecting a redistribution of intracellular Ca2+ or by increasing the response of a Ca2+ -sensitive effector system, but not by enhancing agonist-induced Ca2+ uptake. J. Endocr. (1988) 117, 293–298

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Activation of protein kinase C inhibits calcium-activated potassium channels in rat pituitary tumour cells.

The Journal of Physiology ◽

10.1113/jphysiol.1996.sp021413 ◽

1996 ◽

Vol 493 (3) ◽

pp. 665-672 ◽

Cited By ~ 57

Author(s):

M J Shipston ◽

D L Armstrong

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Potassium Channels ◽

Pituitary Tumour ◽

Tumour Cells ◽

Kinase C ◽

Rat Pituitary ◽

Calcium Activated Potassium Channels

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Human chorionic somatomammotropin and growth hormone gene expression in rat pituitary tumour cells is dependent on proximal promoter sequences

Nucleic Acids Research ◽

10.1093/nar/17.11.4327 ◽

1989 ◽

Vol 17 (11) ◽

pp. 4327-4337 ◽

Cited By ~ 25

Author(s):

Mark W. Nachtigal ◽

Barbara E. Nickel ◽

Margaret E. Klassen ◽

Wengang Zhang ◽

Norman L. Eberhardt ◽

...

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Pituitary Tumour ◽

Tumour Cells ◽

Proximal Promoter ◽

Growth Hormone Gene ◽

Promoter Sequences ◽

Rat Pituitary ◽

Chorionic Somatomammotropin

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Effects of glucocorticosteroids on prolactin and growth hormone production and characterization of the intracellular hormone receptors in rat pituitary tumour cells

Acta Endocrinologica ◽

10.1530/acta.0.0950319 ◽

1980 ◽

Vol 95 (3) ◽

pp. 319-327 ◽

Cited By ~ 16

Author(s):

Oddvar Naess ◽

Egil Haug ◽

Kaare Gautvik

Keyword(s):

Growth Hormone ◽

Hormone Receptors ◽

Pituitary Tumour ◽

Tumour Cells ◽

Scatchard Analysis ◽

Hormone Production ◽

Single Class ◽

High Affinity ◽

Rat Pituitary

Abstract. The effect of corticosterone and dexamethasone on the production of growth hormone and prolactin was studied in rat pituitary tumour cells (GH3-cells) in culture. Corticosterone and dexamethasone caused a dose-dependent stimulation of growth hormone synthesis, and the highest concentration (10−6 mol/l) increased growth hormone levels to 250% of controls. This concentration, however, decreased prolactin synthesis to 25% of the control values. The cytosol fractions from monolayer cultures as well as from tumours of GH3-cells were found to possess receptor molecules for glucocorticoid hormones, having a sedimentation constant close to 8 S in a salt-free buffer and 4 S in the presence of 0.5 mol/l KCL. Isoelectric point of the receptor was 5.8. Scatchard analysis showed one single class of binding sites with high affinity (Kd 2.1 ± 0.4 (sd × 10−9 mol/l). Studies on the steroid specificity revealed that dexamethasone had the highest affinity for the receptor. Corticosterone, cortisol and progesterone had also high affinity, whereas testosterone and oestradiol-17β had no significant affinity for the receptors. After in vivo administration of [3H]dexamethasone to GH3 tumour-bearing rats, radioactivity could be extracted from purified nuclei bound to 4 S macromolecules. The presence of receptors for glucocorticosteroid hormones in the GH3-cells, suggests that these hormones may alter growth hormone and prolactin production at the anterior pituitary level.

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Bombesin stimulates prolactin secretion from cultured rat pituitary tumour cells (GH4C1) via activation of phospholipase C

Regulatory Peptides ◽

10.1016/0167-0115(87)90274-6 ◽

1987 ◽

Vol 19 (3-4) ◽

pp. 169-182 ◽

Cited By ~ 12

Author(s):

T. Bjøro ◽

P.A. Torjesen ◽

B.C. Østberg ◽

O. Sand ◽

J-G. Iversen ◽

...

Keyword(s):

Phospholipase C ◽

Pituitary Tumour ◽

Prolactin Secretion ◽

Tumour Cells ◽

Rat Pituitary

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Interaction between insulin and thyroid hormone in rat pituitary tumour cells: insulin attenuates tri-iodothyronine-induced growth hormone mRNA levels

Journal of Endocrinology ◽

10.1677/joe.0.1370107 ◽

1993 ◽

Vol 137 (1) ◽

pp. 107-114 ◽

Cited By ~ 3

Author(s):

D. Prager ◽

M. M. Weber ◽

S. Gebremedhin ◽

S. Melmed

Keyword(s):

Protein Synthesis ◽

Insulin Treatment ◽

De Novo ◽

Pituitary Tumour ◽

Tumour Cells ◽

Transcriptional Level ◽

Pituitary Cells ◽

Mrna Levels ◽

Insulin Effect ◽

Rat Pituitary

ABSTRACT Insulin has previously been shown to inhibit basal and stimulated rat GH (rGH) secretion as well as basal GH transcription in rat pituitary cells. The effect of physiological doses of insulin on tri-iodothyronine (T3)-stimulated GH mRNA levels in rat pituitary tumour cells was therefore examined. Insulin (7 nmol/l) suppressed T3-stimulated GH mRNA levels in GC and GH3 rat pituitary tumour cells by 58%. This inhibitory effect of insulin on T3-stimulated GH mRNA levels was already present after 24 h of treatment, and persisted for at least 48 h after insulin treatment was withdrawn. The effect of insulin on GH mRNA was selective, as rat prolactin mRNA was stimulated by insulin and T3 in the same cells. Treatment of cells with cycloheximide (10 μmol/l) did not alter the attenuation of GH mRNA levels by insulin, indicating that the insulin effect is independent of new protein synthesis. When de-novo mRNA synthesis was blocked with actinomycin D (4 μg/ml) for up to 7 h, an additional decrease in the relative amount of GH mRNA levels was observed after 24, 48 and 72 h of insulin treatment, indicating that an effect of insulin on GH mRNA stability is likely. The results show that physiological doses of insulin selectively attenuate the stimulatory effect of T3 on GH mRNA levels. This suppressive effect of insulin occurs independently of protein synthesis and is presumably mediated both at a transcriptional and post-transcriptional level. Journal of Endocrinology (1993) 137, 107–114

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The stimulation of phosphorylation of intracellular proteins in GH3 rat pituitary tumour cells by phorbol esters of distinct biological activity

FEBS Letters ◽

10.1016/0014-5793(87)80431-3 ◽

1987 ◽

Vol 224 (1) ◽

pp. 109-116 ◽

Cited By ~ 5

Author(s):

S.F. Brooks ◽

F.J. Evans ◽

A. Aitken

Keyword(s):

Biological Activity ◽

Phorbol Esters ◽

Pituitary Tumour ◽

Tumour Cells ◽

Rat Pituitary ◽

Intracellular Proteins ◽

Stimulation Of

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Membrane Oestrogen Receptors on Rat Pituitary Tumour Cells: Immuno-Identification and Responses to Oestradiol and Xenoestrogens

Experimental Physiology ◽

10.1111/j.1469-445x.1999.01903.x ◽

1999 ◽

Vol 84 (6) ◽

pp. 1013-1022 ◽

Cited By ~ 64

Author(s):

Cheryl S. Watson ◽

Celeste H. Campbell ◽

Bahiru Gametchu

Keyword(s):

Pituitary Tumour ◽

Tumour Cells ◽

Oestrogen Receptors ◽

Rat Pituitary

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Metabolism of inositol bis-, tris-, tetrakis- and pentakis-phosphates in GH3 cells

Biochemical Journal ◽

10.1042/bj2500493 ◽

1988 ◽

Vol 250 (2) ◽

pp. 493-500 ◽

Cited By ~ 32

Author(s):

N M Dean ◽

J D Moyer

Keyword(s):

Inositol Phosphates ◽

Pituitary Tumour ◽

Tumour Cells ◽

Gh3 Cells ◽

Rat Pituitary ◽

Potential Sources ◽

A Minor ◽

Gh3 Cell

Previous studies demonstrated a multiplicity of isomers of inositol phosphates in GH3 rat pituitary tumour cells. In order to determine their origin, we have investigated the metabolism of radiolabelled inositol phosphates (IPn) in GH3 cell homogenates by using h.p.l.c. I(1,4,5)P3 is either phosphorylated to I(1,3,4,5)P4 (in the presence of ATP) or dephosphorylated to I(1,4)P2 (in the absence of ATP). I(1,4)P2 is dephosphorylated to I(4)P (greater than 95%). I(1,3,4,5)P4 hydrolysis yields two products. By using dual-labelled [32P, 3H]I(1,3,4,5)P4 with 32P in either the 3 or the 4/5 position, we have identified the probable configuration of these isomers. The predominant (greater than 97%) IP3 formed is I(1,3,4)P3, with a minor I(1,4,5)P3 peak. Subsequent I(1,3,4)P3 hydrolysis yields two IP2 isomers [the major (approximately equal to 85%) is I(3,4)P2; the minor (approximately equal to 15%) is I(1,3)P2] and two IP isomers (the major (approximately equal to 90%) is I(3)P [L-I(1)P], the minor I(4)P). IP5 is very slowly dephosphorylated to and IP4 of undetermined isomeric configuration. We have also examined GH3 cell lipids for the presence of phosphoinositides either more highly phosphorylated than PIP2 (as potential sources of the IP4/IP5 and IP6 in these cells) or phosphorylated in positions other than 1, 4 and 5, and have been unable to find evidence of either. These data suggest two main routes of metabolism for I(1,4,5)P3 in GH3 cells: either (1) phosphorylation to I(1,3,4,5)P4, and the subsequent consecutive dephosphorylation to I(1,3,4)P3, I(3,4)P2 and finally L-I(1)P [D-I(3)P]; or (2) dephosphorylation to I(1,4)P2 and, subsequently, I(4)P.

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