Differential effects of estrogen and estrogen receptor antagonist, ⅡCI 182780 on the expression of Calbindin-D9k in rat pituitary prolactinoma GH3 cells / 中华内分泌外科杂志

Objective To detect the effects of 17 β-estradiol(E2)on the expression of Calbindin-D9k (CaBP-9k) in pituitary GH3 cells,and to investigate the antagonistic effect of a selective estrogen receptor antagonist,ⅡCI 182780 on CaBP-9k expression.Methods A rat pituitary prolactinoma cell line,GH3 cell was used as the in vitro model.The localization of CaBP-9k in GH3 cells was observed by immunofluorescence.GH3 cells were cultured with exogenous E2-added medium for 24 hours,and the concentrations of E2 were 10-8,10-9,10-10M,respectively.mRNA and protein expression levels of CaBP-9k in different groups were analyzed by RT-PCR and Western blot analysis.The estrogen receptor antagonist,and ⅡCI 182780 was added to GH3 cells before E2 administration (10-8M)with the concentration of 10-6M,in order to investigate the regulation of ER-mediated pathway on the expression of CaBP-9k.Immunoprecipitation was used to detect the interaction between CaBP-9k and ERα.Results E2 had significant stimulatory effect on the CaBP-9k expression of GH3 cells in a dose dependent manner,and the expression level of CaBP-9k was higher when treated with a higher concentration of E2.ⅡCI 182780 could suppress the stimulatory effect of E2 on the CaBP-9k expression of GH3 cells.The expression level of CaBP-9k was significantly reduced by coadministration of E2 with ⅡCI 182780 in GH3 cells,which meant the CaBP-9k expression was mediated through ERα pathway.The immunoprecipitation results further illustrated the fact that CaBP-9k could directly interact with ERα,and E2 could increase the interaction between CaBP-9k and ERα.Conclusion Estrogen might induce CaBP-9k expression via ERα mediated pathway and CaBP-9k could directly combine with ERα,suggesting that CaBP-9k might be involved in the biological effects mediated by ER pathway in GH3 cells.

Aqueous leaf extract of Averrhoa carambola L. (Oxalidaceae) reduces both the inotropic effect of BAY K 8644 on the guinea pig atrium and the calcium current on GH3cells / Extrato aquoso das folhas de Averrhoa carambola L. (Oxalidaceae) reduz tanto o efeito inotrópico do BAY K 8644 em átrio de cobaia, quanto a corrente de cálcio em células GH3

It was previously showed that aqueous leaf extract (AqEx) of Averrhoa carambola depresses the guinea pig atrial inotropism. Therefore, experiments were carried out on guineapig left atrium and on pituitary GH3 cells in order to evaluate the effect of AqEx on the cellular calcium infl ux. The atrium was mounted in an organ chamber (5 mL, Tyrode, 27 ± 0.1 °C, 95% O2, 5 % CO2), stretched to 10 mN, and paced at 2 Hz (0.5 ms, 400 V) and GH3 cells were submitted to a whole cell voltage clamp confi guration. In the atrium, the AqEx (1500 μg/mL) shifted to the right the concentration-effect curve of the positive inotropic effect produced by (±) BAY K 8644, an L-type calcium channel agonist. The AqEx increased EC50 (concentration required to promote 50% of the maximum effect) of the inotropic effect of BAY K 8644 from 7.8 ± 0.38 to 115.1 ± 0.44 nM (N = 3; p < 0.05). In GH3 cells assayed with 500 μg/mL of AqEx, the L-type calcium inward current declined 30 % (from 282 to 190 pA). Nevertheless, the extract did not change the voltage correspondent to the peak current. These data suggest that, at least in part, the negative inotropic effect of AqEx on the guinea pig atrium is due to a reduction of the L-type calcium current.

Em estudo prévio mostrou-se que o extrato aquoso das folhas de Averrhoacarambola (ExAq) reduziu o inotropismo atrial da cobaia. Por isso, este trabalho avaliou se o ExAq interfere com o infl uxo de cálcio através da membrana celular. A investigação foi conduzidaem átrio esquerdo de cobaia, montado em cuba (5 mL, Tyrode, 27 ± 0,1 °C, 95 % O2, 5 % CO2), estirado para uma tensão de repouso de 10 mN e submetido a uma estimulação de 2 Hz (0,5 ms, 400 V). O efeito do ExAq sobre a entrada de cálcio nas células foi avaliado em átrio de cobaia e em células GH3, estas submetidas a ‘patch clamp’ na confi guração ‘whole cell’. No átrio, o ExAq (1500 μg /mL) deslocou para direita a curva concentração-efeito do (±) BAY K 8644 (agonista dos canais de cálcio tipo-L), aumentando a CE50 (concentração capaz de produzir 50 % do efeito máximo) de 7,8 ± 0,38 para 115,1 ± 0,44 nM (N = 3, p < 0,05). Em células GH3, este extrato (500 μg /mL) reduziu de 282 para 190 pA (30 %) a corrente de cálcio, sem contudo alterar a voltagem de pico da curva desta corrente. Estes resultados mostram que, pelo menos em parte, o efeito inotrópico negativo do ExAq em átrio de cobaia se deve a uma diminuição do infl uxo de cálcio pelos canais tipo-L.

Changes in Somatostatin Receptor mRNA Levels by G Protein Mutation in GH3 Cells Which Show Responsiveness to Growth Hormone-Releasing Hormone / 대한내분비학회지

BACKGROUNDS: GH3 cells lack growth hormone(GH)-releasing hormone(GHRH) receptors. In this study, GH3 cells permanently transfected with human GHRH receptor cDNA(GH3-GHRHR cells), were established in order to examine the effects of GHRH and G protein mutation(gsp oncogene) on the levels of somatostatin receptor mRNA. METHODS: GH3 cells were permanently transfected with a plasmid expressing human GHRH receptor cDNA. The GHRH receptor mRNA was detected by RT-PCR. The responsiveness to GHRH was evaluated using a GHRH binding assay, Western blot analysis, Northern blot analysis, and measurements of the intracellular cAMP levels and GH release. Cells were transiently transfected with the gsp oncogene, and then treated with GHRH or octreotide for 4h. The sst1 and sst2 mRNA levels were measured using real-time RT-PCR analyses. RESULTS: GHRH receptor mRNA was detected in the GH3 cells permanently transfected with human GHRH receptor cDNA. The GHRH binding assay showed that GHRH was bound to the GH3-GHRHR cells. The GHRH treatment increased the intracellular cAMP levels, GH release, GH mRNA levels, and MAPK activity, as well as the levels of sst1 and sst2 mRNA. Transient expression of the gsp oncogene for 48h increased the cAMP, GH release, and levels of sst1 and sst2 mRNA. In the gsp-transfected GH3-GHRHR cells, GHRH stimulation resulted in decreases in the magnitude of the increase in the levels of sst1 and sst2 mRNA compared to those transfected with a control vector. Octreotide treatment did not alter the levels of sst1 and sst2 mRNA in either the control or gsp-transfected cells. CONCLUSION: These results suggest that GH3 cells permanently transfected with the GHRH receptor are useful in the in vitro studies on the actions of GHRH. The gsp oncogene was shown to increases the levels of sst1 and sst2 mRNA in GH3 cells, but these findings are unlikely to be the major mechanism by which gsp-positive pituitary tumors show a greater response to somatostatin. The discrepancy between the in vivo and these in vitro results should be examined further.

Gene Expression of the Somatostatin Receptors, Gi2 alpha and Pit-1 alpha in GH3 Cells Permanently Transfected with a Mutant Gs alpha Gene / 대한내분비학회지

BACKGROUND: Cyclic AMP stimulates the expression of the somatostatin (SRIF) receptor (sst1-5) and human growth hormone (GH)-secreting pituitary tumors with the gsp oncogene which increases intracellular cAMP levels, and shows a good inhibitory response of the GH to SRIF. Taken together, we hypothesized that the gsp oncogene may increase the SRIF receptor expression or and factors related to the postreceptor signal transduction of the SRIF, in order to enhance its responsiveness to SRIF. To test this hypothesis, we investigated if the gsp oncogene could increase the sst1, sst2, Gi2 alpha, and pit-1 alpha gene expression in GH3 cells. METHODS: GH3 cells were permanently transfected with the plasmid expressing Gs alpha gene, where the arginine of codon 201 was replaced with histidine. Intracellular cAMP levels and GH concentrations were measured by radioimmunoassays. Gene expressions of the sst1, sst2, Gi2 alpha, and pit-1 alpha were determined by RT-PCR. RESULTS: Intracellular cAMP levels and medium GH release were increased by 1.7 and 2.7-fold in GH3 cells expressing the gsp oncogene, respectively. In GH3 cells expressing the gsp oncogene, the sst1 mRNA levels were decreased, whereas those of the sst2, Gi2 alpha and pit-1 alpha mRNA were increased. A 4-h forskolin (10 M) stimulation remarkably increased the sst1 and sst2 mRNA levels in GH3 cells expressing wild and mutant Gs alpha . However, forskolin did not affect the Gi2 alpha and pit-1 alpha mRNA levels. In contrast, SRIF (1 M, 2 h) decreased the sst2 mRNA levels only in GH3 cells expressing the gsp oncogene. CONCLUSION: These results suggest that higher expressions of sst2, Gi2 alpha, and pit-1 alpha, induced by the gsp oncogene may be a mechanism by which gsp-positive pituitary tumors show a greater response to SRIF. The discrepancy between these and in vivo results should be explored further.

Effects of Polylysine Coating on GH3 Rat Pituitary Tumor Cells in Culture / 대한해부학회지

GH3 cells are derived from rat pituitary tumor cells that secrete prolactin and growth hormone, and important in studying prolactin-secreting pitutary tumors. This study was performed to examine the effects of polylysine on growth and differentiation of GH3 cells by means of (a) cell attachment assay (b) cell count and bromodeoxyuridine labeling and (c) immunohistochemistry for prolactin in the absence or presence of epidermal growth factor (EGF). Cell shape, attachment to the culture surface and growth of GH3 cells were not affected by polylysine coating. The percentages of prolactin-immunoreactive cells were higher in the cells cultured on the polylysine-coated surface compared to those on the plastic surface. Cell number and BrdU incorporation were lower in the EGF-treated cells on both culture surfaces. The results provided basic information on the effects of polylysine coating on GH3 cells in culture and suggested that polylysine coating was useful for the study on GH3 cells because it enhanced cell differentiation as well as it provided stronger attachment than plastic surfaces.