DNA sequences required for expression of the LHβ promoter in primary cultures of rat pituitary cells

1990 ◽  
Vol 74 (2) ◽  
pp. 101-107 ◽  
Author(s):  
Kyoon E. Kim ◽  
Kathleen H. Day ◽  
Paul Howard ◽  
Stephen R.J. Salton ◽  
James L. Roberts ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Primary Cultures ◽  
Pituitary Cells ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

Mechanism of the prolactin rebound after dopamine withdrawal in rat pituitary cells

1993 ◽  
Vol 265 (1) ◽  
pp. E145-E152 ◽  
Author(s):  
C. Chen ◽  
J. Zhang ◽  
J. M. Israel ◽  
I. J. Clarke ◽  
J. D. Vincent
Keyword(s):  
Primary Cultures ◽  
Rebound Effect ◽  
Prolactin Secretion ◽  
Maximum Effect ◽  
Pituitary Cells ◽  
Channel Blockade ◽  
Short Term ◽  
Prolactin Release ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

To study the mechanism underlying the effect of dopamine withdrawal on prolactin release, continuous perfusion experiments were performed on rat lactotroph-enriched primary cultures. Removal of dopamine (10(-7) M) after a short-term application (15 min) produced a rebound of prolactin secretion, which was enhanced by pretreatment of the cell culture with 17 beta-estradiol (10(-8) M for 48 h). Ca2+ channel blockade by Co2+ (1 mM) abolished the rebound in prolactin release. An increase in intracellular adenosine 3',5'-cyclic monophosphate by either forskolin (5 microM) or 3-isobutyl-1-methylxanthine (100 microM) enhanced the prolactin rebound after dopamine withdrawal. Application of thyrotropin-releasing hormone (10(-7) M) increased the prolactin rebound after dopamine withdrawal with a maximum effect obtained by commencing treatment immediately after removal of dopamine. Pretreatment of cell cultures with pertussis toxin (100 ng/ml, for 10 h) totally abolished the effects of dopamine on prolactin secretion. The dopamine agonist bromocriptine (10(-9) M) significantly decreased prolactin secretion, but no rebound effect was observed after its removal. We conclude that the rebound of prolactin release after dopamine treatment involves the influx of Ca2+.

Characterization of a hyperpolarization-activated cation current in rat pituitary cells

1997 ◽  
Vol 272 (3) ◽  
pp. E405-E414 ◽  
Author(s):  
S. M. Simasko ◽  
S. Sankaranarayanan
Keyword(s):  
Primary Cultures ◽  
Gh3 Cells ◽  
Pituitary Cells ◽  
Sodium Permeability ◽  
Cation Current ◽  
Whole Cell Patch Clamp ◽  
Bath Application ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

Whole cell patch-clamp techniques were used on clonal pituitary cells (GH3) and primary cultures of somatotrophs and lactotrophs to study currents that would be active at or below voltages for the threshold for action potential generation. When GH3 cells were held at -60 mV and pulsed to -120 mV, a slow-activating sustained inward current was observed (-16.5 +/- 1.5 pA in physiological baths, n = 72; approximately 1 s to half-maximal activation, voltage for 50% activation - 101 mV). The current was insensitive to bath application of 10 mM tetraethylammonium, 10 mM 4-aminopyridine, and 1 mM barium but was completely blocked by 3 mM cesium. The current was found to be a mixed cation current with a sodium permeability of 0.29 relative to potassium. These properties indicate that the current belongs to the hyperpolarization-activated cation current (Ih), or I(f), family of currents. However, the current was not altered by the addition of adenosine 3',5'-cyclic monophosphate (cAMP) to the pipette or forskolin to the bath. A similar but smaller current was observed in 15 of 16 somatotrophs but in only 1 of 9 lactotrophs. Application of cesium to spontaneously spiking GH3 cells or somatotrophs had no effect. However, cesium did block an inward holding current observed at -80 mV. These results demonstrate that the I(h) in pituitary cells does not serve as a pacemaking current but suggest that it may influence membrane potential responses when somatotrophs become hyperpolarized.

Cyclic adenosine nucleotides and growth hormone-releasing factor increase cytosolic growth hormone messenger RNA levels in cultured rat pituitary cells

1986 ◽  
Vol 110 (1) ◽  
pp. 51-57 ◽  
Author(s):  
R. N. Clayton ◽  
L. C. Bailey ◽  
S. D. Abbot ◽  
A. Detta ◽  
K. Docherty
Keyword(s):  
Growth Hormone ◽  
Gene Transcription ◽  
Messenger Rna ◽  
Primary Cultures ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Rat Pituitary ◽  
Cdna Hybridization ◽  
Adenosine Nucleotides ◽  
Rat Pituitary Cells

ABSTRACT The cellular mechanisms involved in GH biosynthesis have been investigated by the measurement of steady-state levels of cytosolic GH messenger RNA (mRNA) in primary cultures of rat pituitary cells using an RNA–complementary DNA (cDNA) hybridization assay. Growth hormone mRNA–cDNA hybridization increased in a linear manner with increasing cytosol concentration. Cellular GH mRNA levels rose by an average of 2·4-fold (range, 1·6–3·3; n = five experiments) after exposure to GH-ieleasing factor (GRF(1–40); 10 nmol/l) for 3 days. Treatment with GRF increased the release of GH into the culture medium, and depleted the cellular GH content by 40%. Total GH (in the medium plus cells) after GRF treatment increased by between 1·5- and 3·8-fold, a magnitude similar to the increase in GH mRNA levels. Treatment of cells with dibutyryl adenosine 3′:5′-cyclic monophosphate (1 mmol/l) or forskolin (5 μmol/l) increased the levels of cytosolic GH mRNA by between 1·6- and 4·7-fold. These agents increased GH release into the medium, depleted cellular GH content and increased total GH in the system to the same extent as GRF (10 nmol/l). These data demonstrate that cyclic adenosine nucleotides may mediate the GRF induction of GH gene transcription. In addition, we have shown that increases in the levels of cellular GH mRNA are reflected by increased GH biosynthesis, suggesting that the regulation of hormone gene transcription is one cellular site for the control of hormone biosynthesis and, ultimately, hormone available for release. J. Endocr. (1986) 110, 51–57

Effects of tri-iodothyronine, cortisol and transcriptional inhibitors on vitamin D3-enhanced thyrotrophin secretion by rat pituitary cells in vitro

1989 ◽  
Vol 121 (3) ◽  
pp. 451-458 ◽  
Author(s):  
M. C. d'Emden ◽  
J. D. Wark
Keyword(s):  
Primary Cultures ◽  
Relative Increase ◽  
Pituitary Cells ◽  
Dihydroxyvitamin D ◽  
Rat Pituitary ◽  
Tsh Secretion ◽  
Dependent Inhibition ◽  
Rat Pituitary Cells

ABSTRACT The hormone 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) has been shown to selectively enhance agonist-induced TSH release in the rat thyrotroph in vitro. The interaction of 1,25-(OH)2D3 with tri-iodothyronine (T3) and cortisol was studied in primary cultures of dispersed anterior pituitary cells. TRH (1 nmol/l)-induced TSH release over 1 h was enhanced by 70% (P<0·01) following exposure to 10 nmol 1,25-(OH)2D3/l for 24 h. Pretreatment with T3 (1 pmol/l–1 μmol/l) for 24 h caused a dose-dependent inhibition of TRH-induced TSH release. Net TRH-induced TSH release was inhibited by 85% at T3 concentrations of 3 nmol/l or greater. Co-incubation with 1,25-(OH)2D3 resulted in enhanced TRH-induced TSH release at all T3 concentrations tested (P<0·001). The increment of TRH-induced TSH release resulting from 1,25-(OH)2D3 pretreatment was equivalent in the presence or absence of maximal inhibitory T3 concentrations. At 1 nmol T3/1, there was a two- to threefold relative increase in 1,25-(OH)2D3-enhanced TRH-induced TSH release. Incubation with cortisol (100 pmol/l–100 nmol/l) had no effect on basal or TRH-induced TSH release, nor did it alter 1,25-(OH)2D3-enhanced TRH-induced TSH release when added 24 h before, or at the time of addition of 1,25-(OH)2D3. Actinomycin D and α-amanitin abolished 1,25-(OH)2D3-enhanced TSH secretion. These data demonstrate that the action of 1,25-(OH)2D3 in the thyrotroph required new RNA transcription, and was not affected by cortisol. In the presence of T3, the response of the thyrotroph to TRH induced by 1,25-(OH)2D3 was increased. We have shown that 1,25-(OH)2D3 has significant effects on the action of TRH and T3 in vitro. These findings support the proposal that 1,25-(OH)2D3 may modulate TSH secretion in vivo. Journal of Endocrinology (1989) 121, 451–458

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