• 한국발생생물학회지:발생과생식
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• 제4권2호
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• pp.237-242
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• 2000

흰쥐 시상하부에서 합성ㆍ분비되어 뇌하수체 전엽에서의 growth hormone (GH) 분비를 촉진하는 growth hormone releasing hormone (GHRH)이 시상하부 이외 조직들 (extrahypothalamic tissues)인 태반, 생식소, 그리고 뇌하수체 전엽에서도 발현됨이 보고되었다. 본 연구는 흰쥐 뇌하수체 전엽에서 발현되는 GHRH의 기능을 조사하기 위해 i)세포 배양을 시행하면서 GHRH의 세포내 함량, 분비 그리고 세포분획법 (cell-fractionation)을 사용하여 분리한 뇌하수체 세포 유형별로 GHRH 함량을 방사면역측정법으로 조사하였고, ii)체외배양 중인 뇌하수체 전엽세포의 증식에 미치는 GHRH의 효과를 측정하기 위해 [$^3$H] thymidine incorporation assay를, 그리고 iii) GHRH의 세포분열 촉진 효과와 세포내 c-fos 유전자 발현과의 상관관계를 조사하기 위해 northern blot analysis를 시행하였다. GHRH 방사면역측정법을 시행한 결과 상당량의 GHRH-like 분자들이 흰쥐 뇌하수체 전엽내에 존재하고, 체외 세포배양시 분비됨을 관찰하였다. 세포분획을 사용한 실험에서 GHRH 함량은 gonadotrope, somatotrope, lactotrope 그리고 thyrotrope 순으로 나타났다. 이 러한 결과는 흰쥐 뇌하수체 전엽에서 생성된 GHRH가 국부적인 조절인자, 특히 상이한 유형의 세포들 간의 상호조절 (cross-talk)을 통해 뇌하수체 전엽에서의 세포분열과 분화, 그리고 기능조절에 관여할 가능성을 보여주었다. GHRH는 체외 배양중인 뇌하수체 전엽세포의 [$^3$H] thymidine incorporation을 농도의존적으로 증가시켰으며, 이러한 GHRH의 세포분열 촉진 효과는 예상대로 세포내 oncogene 활성 의 증가를 통해 일어나는 것임을 c-fos northrn blot으로 확인하였다. 결론적으로, 본 연구는 흰쥐 뇌하수체 전엽에서 합성되는 GHRH가 paracrine 또는 autocrine 기작으로 GH의 분비 촉진 이외에도 세포분열의 조절함을 시사하는 것이다.

• 대한수의학회지
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• 제41권1호
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• pp.1-6
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• 2001

Pituitary adenylate cyclase activating polypeptide (PACAP)는 양의 뇌하수체에서 처음 분리 되었고, 뇌하수체 전엽세포의 cAMP의 생성을 자극하며, 흰쥐고환의 정자형성과 steroid 호르몬 형성에 관련한다고 알려져 있다. 이 연구는 성숙한 흰쥐의 고환에서 PACAP mRNA와 그 단백질의 분포를 조사하여 아래와 같은 결론을 얻었다. PACAP mRNA와 그 단백질은 흰쥐의 정세관에서 정자세포의 생성단계에 따라 특이적으로 발현되었다. 이들은 정세관의 발달단계 중 III~VII 기의 정자세포에서 발현되었고, 특히 V 기에서 초기 VII 기의 원형의 정자세포에서 가장 강하게 발현되었다. 이러한 결과는 흰쥐고환의 발달단계에 있는 정자세포에서 합성된 PACAP이 정자형성에 관련된다는 것을 나타내므로, PACAP이 고환의 기능에 중요한 역할을 하는 것을 암시한다.

• 한국발생생물학회지:발생과생식
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• 제2권2호
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• pp.189-196
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• 1998

Growth Hormone Releasing Hormone (GHRH)은 척추동물의 시상하부로부터 합성, 분비되어 시상하부-뇌하수체간의 문맥계를 통해 뇌하수체 전엽에 작용하여 Growth Hormone (GH)의 분비를 촉진한다. 시상하부에서 발현되는 일부 Releasing Hormone 들이 여러 시상하부외 조직에서도 검출되고 조직특이적인 기능을 수행한다는 사실이 여러 연구자들에 의해 밝혀졌다. 이러한 사실들을 배경으로 본 연구자는 GHRH가 흰쥐의 뇌하수체 전엽과 뇌하수체로부터 유래된 종양세포주들에서 발현될 가능성을 조사하였다. GHRH 펩타이드와 mRNA의 존재와 구조를 규명하기 위하여 뇌하수체와 배양 세포를 사용하여 GHRH immunocytochemistry, 방사면역측정법, GHRH PCR과 RNase protection assay를 시행하였다. Immunocytochemistry의 결과 gonadotrope (대형)와 somat-olactotrope (중간형)로 추정되는 세포들에서 GHRH 염색이 나타났고, Somatolactotrope성 종양세포인 GH3 cell 추출물에서 immunoreactive GHRH가 방사면역측정법으로 검출되었다. 3'rapid amplification of cDNA end (3'-RACE)를 시행한 결과, 흰쥐 뇌하수체에 GHRH transcript가 존재하고, 그 3'end 부분이 다른 조직내의 GHRH와 동일함을 확인하였다. GHRH RT-PCR에서도 뇌하수체와 종양세포주들인 $\alpha$T3 cell (gonadotrope성)과 GH3 cell에서 예상 산물들이 증폭되었다. RNase protection assay를 시행한 결과 난소절제에 의해 뇌하수체내 GHRH 유전자 발현이 증가됨을 확인하였다. 이상의 결과는 GHRH가 뇌하수체 전엽의 gonadotrope와 somatotrope에서 발현되고, paracrine 또는 autocrine조절물질로 작용하여 GH 분비 외에도 뇌하수체 전엽 세포들의 분화와 분열등에 관여함을 시사한다.

• The Korean Journal of Physiology and Pharmacology
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• 제23권3호
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• pp.171-179
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• 2019

Pituitary tumors are usually benign but can occasionally exhibit hormonal and proliferative behaviors. Dysregulation of the G1/S restriction point largely contributes to the over-proliferation of pituitary tumor cells. F-box protein S-phase kinase-interacting protein-2 (SKP2) reportedly targets and inhibits the expression of $p27^{Kip1}$, a well-known negative regulator of G1 cell cycle progression. In this study, SKP2 expression was found to be upregulated while $p27^{Kip1}$ expression was determined to be downregulated in rat and human pituitary tumor cells. Furthermore, SKP2 knockdown induced upregulation of $p27^{Kip1}$ and cell growth inhibition in rat and human pituitary tumor cells, while SKP2overexpression elicited opposite effects on $p27^{Kip1}$ expression and cell growth. The expression of microRNA-186 (miR-186) was reported to be reduced in pituitary tumors. Online tools predicted SKP2 to be a direct downstream target of miR-186, which was further confirmed by luciferase reporter gene assays. Moreover, miR-186 could modulate the cell proliferation and $p27^{Kip1}$-mediated cell cycle alternation of rat and human pituitary tumor cells through SKP2. As further confirmation of these findings, miR-186 and $p27^{Kip1}$ expression were downregulated, while SKP2 expression was upregulated in human pituitary tumor tissue samples; thus, SKP2 expression negatively correlated with miR-186 and $p27^{Kip1}$ expression. In contrast, miR-186 expression positively associated with $p27^{Kip1}$ expression. Taken together, we discovered a novel mechanism by which miR-186/SKP2 axis modulates pituitary tumor cell proliferation through $p27^{Kip1}$-mediated cell cycle alternation.

• 생약학회지
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• 제9권1호
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• pp.33-39
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• 1978

The present study is involved with the prolactin secretion from anterior pituitary gland by ginseng saponin since it was handled down by tradition that ginseng might influence the milk secretion when it was given to nursing mother. To investigate the effect of saponin on the prolactin production or release from the anterior pituitary gland, cell culture study and whole animal studies were carried out. For the cell culture study, enzymatically dispersed anterior pituitary cells of rat anterior pituitary gland in HEPES buffers containing trypsin were used. Ginseng saponin was added to the culture media and the amount of prolactin produced in the cell culture media was determined by radloimmunoassay(RIA) technique. Dose-dependent increases of prolactin with ginseng saponin were observed, whereas, no change was observed without ginseng treatment. For the whole animal study, normal and castrated rats which previously cannulated into the heart via the right juglar vein were used. The prolactin concentration in plasma were determined by using the technique of RIA. In normal rats, prolactin concentration in plasma were elevated dramatically after 1 hour of ginseng saponin administration, whereas, instantaneous increases were observed in castrated rats. For prolactin assay by RIA, NIAMDD Rat Prolactin Kit and NIAMDD Rat Prolactin RP-1 were used as standard. The results indicate that ginseng saponins increase the release of prolactin from the anterior pituitary gland and production of prolactin from the cell in rats.

• 한국동물학회:뉴스레터
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• 제12권2호
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• pp.116.1-116
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• 1995

No Abstract, See Full Text

• 한국동물학회:학술대회논문집
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• 한국동물학회 1995년도 한국생물과학협회 학술발표대회
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• pp.252.1-252
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• 1995

No Abstract, See Full Text

• Clinical and Experimental Reproductive Medicine
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• 제23권3호
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• pp.269-275
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• 1996

Biosynthesis and secretion of anterior pituitary hormones are under the control of specific hypothalamic stimulatory and inhibitory factors. Among them, Growth Hormone Releasing Hormone (GHRH) is the major stimulator of pituitary somatotrophs activating GH gene expression and secretion. Human GHRH is a polypeptide of 44 amino acids initially isolated from pancreatic tumors, and the gene for the hypothalamic form of GHRH is organized into 5 exons spanning over 10 kilobases (kb) on genomic DNA and encodes a messenger RNA of 700-750 nucleotides. Several neuropeptides classically associated with the hypothalamus have been found in the extrahypothalamic regions, suggesting the existence of novel sources, targets and functions. GHRH-like immunoreactivity has been found in several peripheral sites, including placenta, testis, and ovary, indicating that GHRH may also have regulatory roles in peripheral reproductive organs. Furthermore, higher molecular weight forms of the GHRH transcripts were identified from these organs (1.75 kb in testis; 1.75 and >3 kb in ovary). These tissue-specific expression of GHRH gene suggest the existence of unique regulatory mechanism of GHRH expression and function in these organs. In fact, placenta-specific and testis-specific promoters for GHRH transcripts which are located in about 10 kb upstream region of hypothalamic promoter were reported. The use of unique promoters in extrahypothalamic sites could be refered in a different control of GHRH gene and different functions of the translated products in these tissues. Somatotrophs and lactotrophs have been thought to be derived from a common bipotential progenitor, the somatolactotrophs, which give origins to either phenotypes. Although the precise mechanism responsible for the lactotroph differentiation in the anterior pituitary gland has not been yet clalified, there are several candidators for the generation of lactotrophs. In human, the presence of GHRH peptides with different size from authentic hypothalamic form in the normal anterior pituitary and several types of adenoma were demonstrated. Recently our group found the existence of immunoreactive GHRH and its transcript from the normal rat anterior pituitary (gonadotroph> somatotroph> lactotroph), and the GHRH treatment evoked the increased proliferation rate of anterior pituitary cells in vitro. The transgenic mouse models clearly shown that GHRH or NGF overexpression by anterior pituitary cells induced development of pituitary hyperplasia and adenomas particularly GH-oma and prolactinoma. Taken together, we hypothesize that the pituitary GHRH could serve not only as a modulator of hormone secretion but as a paracrine or autocrine regulator of anterior pituitary cell proliferation and differentiation. Interestingly enough, the expression of Pit-1 homeobox gene (the POU class transcription factor) was confined to somatotrophs, lactotrophs and somatolactotrophs in which GHRH receptors are expressed commonly. Concerning the mechanism of somatolactotroph and lactotroph differentiation in the anterior pituitary, we have focused following two possibilities; (1) changes in the relative levels or interactions of both hypothalamic and intrapituitary factors such as dopamine, VIP, somatostatin, NGF and GHRH; (2) alterations of GHRH-GHRH receptor signaling and Pit-1 activity may be the cause of lactotroph differentiation or pituitary hyperplasia and adenoma formation. Extensive further studies will be necessary to solve these complicated questions.

• The Korean Journal of Physiology and Pharmacology
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• 제4권2호
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• pp.81-90
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• 2000

The types of $K^+$ channel which determine the pattern of spontaneous action potential (SAP) were investigated using whole-cell variation of patch clamp techniques under current- and voltage-clamp recording conditions in rat clonal pituitary $GH_3$ cells. Heterogeneous pattern of SAP activities was changed into more regular mode with elongation of activity duration and afterhyperpolarization by treatment of TEA (10 mM). Under this condition, exposure of the class III antiarrhythmic agent E-4031 $(5\;{\mu}M)$ to $GH_3$ cells hardly affected SAP activities. On the other hand, the main $GH_3$ stimulator thyrotropin-releasing hormone (TRH) still produced its dual effects (transient hyperpolarization and later increase in SAP frequency) in the presence of TEA. However, addition of $BaCl_2$ (2 mM) in the presence of TEA completely blocked SAP repolarization process and produced membrane depolarization in all tested cells. This effect was observed even in TEA-untreated cells and was not mimicked by higher concentration of TEA (30 mM). Also this barium-induced membrane depolarization effect was still observed after L-type $Ca^{2+}$ channel was blocked by nicardipine $(10\;{\mu}M).$ These results suggest that barium-sensitive current is important in SAP repolarization process and barium itself may have some depolarizing effect in $GH_3$ cells.

• BMB Reports
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• 제40권6호
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• pp.1016-1020
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• 2007

In this study, dioscin was isolated from Dioscoreae Rhizoma (DR), which is the rhizome of Dioscorea batatas DECNE. that inhabits broad areas of Korea and Japan. To determine whether dioscin induced growth hormone (GH) release, we evaluated its induction effects on GH release both in vitro and in vivo. The 70% methanol extract of DR, and its n-hexane and n-BuOH fractions, induced rat GH (rGH) release in rat pituitary cells 10-fold, 8-fold, and 5-fold higher than the control ($0.36{\pm}0.02 nM$), respectively (p < 0.05 each). The dioscin-induced rGH release of the cells was concentration-dependent and its $ED_{50}$ was $1.14{\times}10^{-5} M$. Within 90 minutes after intravenous administration of $10{\mu}g$/kg (p < 0.05 at $t_{max}$), dioscin caused the greatest increase in rGH concentration ($C_{max}$) in the rat plasma ($34.16{\pm}14.10 ng/ml$) (n = 4), which was twice as high as the control group ($12.88{\pm}3.29 ng/ml$) (n = 27).