scholarly journals Expression of Thyrotropin-Releasing Hormone (TRH) Receptor mRNA in Somatotrophs in the Rat Anterior Pituitary

Endocrinology ◽  
1997 ◽  
Vol 138 (2) ◽  
pp. 827-830 ◽  
Author(s):  
Shuntaro Konaka ◽  
Masanobu Yamada ◽  
Tetsuro Satoh ◽  
Hitoshi Ozawa ◽  
Eri Watanabe ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Thyrotropin Releasing Hormone ◽  
Releasing Hormone ◽  
Receptor Mrna ◽  
Trh Receptor

scholarly journals Cloning and expression of the thyrotropin-releasing hormone receptor from GH3 rat anterior pituitary cells

1992 ◽  
Vol 284 (3) ◽  
pp. 891-899 ◽  
Author(s):  
P de la Peña ◽  
L M Delgado ◽  
D del Camino ◽  
F Barros
Keyword(s):  
Blot Analysis ◽  
Anterior Pituitary ◽  
Functional Expression ◽  
Thyrotropin Releasing Hormone ◽  
Cloning And Expression ◽  
Receptor Protein ◽  
Pituitary Cells ◽  
Releasing Hormone ◽  
Continuous Sucrose Gradient ◽  
Trh Receptor

Functional thyrotropin-releasing hormone (TRH) receptors have been expressed in Xenopus laevis oocytes following the microinjection of total and poly(A)+ RNA from GH3 rat anterior pituitary tumour cells. Under voltage-clamp conditions, application of the peptide induced a biphasic Ca(2+)-dependent chloride current. The amplitude of the initial, fast, component of the response was dependent on the concentration of the hormone and on the amount of mRNA injected. Size fractionation of poly(A)+ RNA on a continuous sucrose gradient and Northern blot analysis indicated that the receptor was encoded by an mRNA of approx. 3.5 kb. A 3.28 kbp cDNA encoding the TRH receptor has been cloned and sequenced. Full functionality of the predicted 412-amino-acid receptor protein was demonstrated by functional expression of cell surface receptors in Xenopus oocytes after both cytoplasmic injection of sense RNA transcribed in vitro from this cDNA and nuclear injection of the cDNA under the control of the Herpes simplex virus thymidine kinase promoter. The predicted protein contains seven putative membrane-spanning domains and shows significant sequence identify with some G-protein-coupled receptors. RNA blot analysis indicates that the mRNA for the TRH receptor is exclusively expressed in the pituitary gland. Expression studies performed with clones in which the 3′ region of the mRNA has been successively shortened indicate that the 3′ terminal region is not an important determinant for efficient functional expression in oocytes.

1,25-Dihydroxyvitamin D3-induced upregulation of the thyrotropin-releasing hormone receptor in clonal rat pituitary GH3 cells

1995 ◽  
Vol 147 (3) ◽  
pp. 397-404 ◽  
Author(s):  
L M Atley ◽  
N Lefroy ◽  
J D Wark
Keyword(s):  
Vitamin D ◽  
Fold Increase ◽  
Thyrotropin Releasing Hormone ◽  
Gh3 Cells ◽  
Pituitary Hormone ◽  
Pituitary Cells ◽  
Hormone Production ◽  
Releasing Hormone ◽  
Rat Pituitary ◽  
Trh Receptor

Abstract 1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) is active in primary dispersed and clonal pituitary cells where it stimulates pituitary hormone production and agonist-induced hormone release. We have studied the effect of 1,25-(OH)2D3 on thyrotropin-releasing hormone (TRH) binding in clonal rat pituitary tumour (GH3) cells. Compared with vehicle-treated cells, 1,25-(OH)2D3 (10 nmol/l) increased specific [3H]MeTRH binding by 26% at 8 h, 38% at 16 h, 35% at 24 h and reached a maximum at 48 h (90%). In dose–response experiments, specific [3H]MeTRH binding increased with 1,25-(OH)2D3 concentration and reached a maximum at 10 nmol/l. Half-maximal binding occurred at 0·5 nmol 1,25-(OH)2D3/l. The vitamin D metabolite, 25-OH D3, increased [3H]MeTRH binding but was 1000-fold less potent than 1,25-(OH)2D3. In equilibrium binding assays, treatment with 10 nmol 1,25-(OH)2D3/l for 48 h increased the maximum binding from 67·4 ± 8·8 fmol/mg protein in vehicle-treated cells to 96·7 ± 12·4 fmol/mg protein in treated cells. There was no difference in apparent Kd (1·08 ± 0·10 nmol/l for 1,25-(OH)2D3-treated and 0·97 ± 0·11 nmol/l for vehicle-treated cells). Molecular investigations revealed that 10 nmol 1,25-(OH)2D3/l for 24 h caused an 8-fold increase in TRH receptor-specific mRNA. Actinomycin D (2 μg/ml, 6 h) abrogated the 1,25-(OH)2D3-induced increase in [3H]MeTRH binding. Cortisol also increased [3H]MeTRH binding but showed no additivity or synergism with 1,25-(OH)2D3. TRH-stimulated prolactin release was not enhanced by 1,25-(OH)2D3. We conclude that the active vitamin D metabolite, 1,25-(OH)2D3, caused a time- and dose-dependent increase in [3H]MeTRH binding. The effect was vitamin D metabolite-specific and resulted from an upregulation of the TRH receptor. Further studies are needed to determine the functional significance of this novel finding. Journal of Endocrinology (1995) 147, 397–404

Influence of terbutaline on TRH-induced prolactin and thyrotropin release in normal subjects

1986 ◽  
Vol 113 (2) ◽  
pp. 204-210
Author(s):  
Sven Röjdmark
Keyword(s):  
Anterior Pituitary ◽  
Normal Subjects ◽  
Thyrotropin Releasing Hormone ◽  
Saline Infusion ◽  
Inhibitory Influence ◽  
Measurable Effect ◽  
Releasing Hormone ◽  
Background Infusion

Abstract. To investigate whether terbutaline (T) influences the release of prolactin (Prl) and/or thyrotropin (TSH) from the anterior pituitary, 25 μg thyrotropin-releasing hormone (TRH) was injected iv in 7 normal subjects who were pre-treated orally with either T or placebo. The TRH-induced Prl response, as reflected by the Prl incremental area, was more pronounced after priming with placebo (2071 ± 606) than after T (1391 ± 434; P < 0.05). In contrast, the TRH-elicited TSH responses did not differ significantly after the two pre-treatments. When TRH was given to 8 additional individuals on iv background infusion of either T or saline, the Prl response was significantly larger during saline (2123 ± 354) than during T infusion (1540 ± 235; P < 0.01), whereas the TSH responses were of similar magnitudes. Six subjects, given 25 μg TRH iv on background infusion of T or saline, were also given propranolol orally before commencement of the T infusion and placebo before the saline infusion. This resulted in similar Prl responses and also in similar TSH responses, during the two background treatments. The results imply that oral as well as iv administration of T has inhibitory influence on human lactotrophs, but lacks measurable effect on thyrotrophs.

Sign in / Sign up

Export Citation Format

Share Document