Regulation of $LH{\beta}$ subunit mRNA by Ovarian Steroid in Ovariectomized Rats

김창미,박덕배,유경자,Kim, Chang-Mee,Park, Deok-Bae,Ryu, Kyung-Za The Korean Society of Pharmacology 1993 대한약리학잡지 Vol.29 No.2

Pituitary LH release has been known to be regulated by the hypothalamic gonadotropin releasing hormone (GnRH) and the gonadal steroid hormones. In addition, neurotransmitters and neuropeptides are actively involved in the control of LH secretion. The alteration in LH release might reflect changes in biosynthesis and/or posttranslational processing of LH. However, little is known about the mechanism by which biosynthesis of LH subunits is regulated, especially at the level of transcription. In order to investigate if ovarian steroid hormones regulate the LH subunit gene expression, ${\alpha}\;and\;LH{\beta}$ steady state mRNA levels were determined in anterior pituitaries of ovariectomized rats. Serum LH concentrations and pituitary LH concentrations were increased markedly with time after ovariectomy. ${\alpha}\;and\;LH{\beta}$ subunit mRNA levels after ovariectomy were increased in a parallel manner with serum LH concentrations and pituitary LH contents, the rise in $LH{\beta}$ subunit mRNA levels being more prominent than the rise in ${\alpha}\;subunit$ mRNA. ${\alpha}\;and\;LH{\beta}$ subunit mRNA levels in ovariectomized rats were negatively regulated by the continuous treatment of ovarian steriod hormones for $1{\sim}4\;days$ and $LH{\beta}\;subunit$ mRNA seemed to be more sensitive to negative feedback of estradiol than progesterone. Treatment of estrogen antagonist, LY117018 or progesterone antagonist, RU486 significantly restroed LH subunit mRNA levels as well as LH release which were suppressed by estradiol or progesterone treatment. These results suggest that ovarian steroids negatively regulate the LH synthesis at the pretranslational level by modulating the steady state levels of ${\alpha}\;and\;LH{\beta}\;subunit$ mRNA and $LH{\beta}\;subunit$ mRNA seemed to be more sensitive to negative feedback action of estradiol than progesterone.

Regulation of Luteinizing Hormone Release and Subunit mRNA by GnRH and Ovarian Steroids in Cultured Anterior Pituitary Cells

김창미,박일선,유경자,Kim, Chang-Mee,Park, Il-Sun,Ryu, Kyung-Za The Korean Society of Pharmacology 1994 대한약리학잡지 Vol.30 No.1

The effects of gonadoropin-releasing hormone (GnRH) and ovarian steroid hormones on the release of luteinizing hormone (LH) and its subunit mRNA levels were investigated in anterior pituitary cells in culture. LH concentration was measured by a specific radioimmunoassay and mRNA levels of u and $LH{\beta}$ subunits by RNA slot blot hybridization assay. GnRH stimulated LH release in a dose-dependent manner from cultured pituitary cells. However, the basal LH release in the absence of GnRH was not changed during the course of 24h culture, strongly suggesting that release of LH is directly controlled by GnRH. The treatment of the pituitary cells with GnRH increased $LH{\beta}$ subunit mRNA levels in a dose-dependent manner, reaching the maximum with $2\;{\times}\;10^{-10}M$ GnRH while no significant increase in ${\alpha}$ subunit mRNA levels was observed after GnRH treatment. Estradiol did not augment GnRH-induced LH release while progesterone augmented GnRH-induced LH release in a dose-dependent manner at the level of pituitary. However, estradiol and progesterone increased basal and GnRH-induced $LH{\beta}$ subunit mRNA levels in a dose-dependent manner. The treatment of estrogen antagonist, LYI17018 blocked the effect of estradiol on GnRH-induced $LH{\beta}$ subunit mRNA levels in a dose-dependent manner while progesterone antagonist, Ru486 tended to block the effect of progesterone on GnRH-induced $LH{\beta}$ subunit mRNA levels. It is therefore suggested that GnRH Playa a major role in LH release and subunit biosynthesis by influencing the steady state $LH{\beta}$ subunit mRNA loves and ovarian steroid hormones modulate subunit biosynthesis via directly acting on pituitary gonadotropes.

흰쥐 수정란 착상시기에 있어서의 호르몬 농도의 변화와 자궁내막의 구조에 관한 연구

윤미정,손성향,김창미,최임순,Yoon, Mi-Chung,Sohn, Seong-Hyang,Kim, Chang-Mee,Choe, Rim-Soon 한국현미경학회 1993 Applied microscopy Vol.23 No.1

The mechanism by which blastocysts implant to uterine endometrium has not been clearly understood. In the present study, the following question was investigated: how are hormonal levels changed and how is uterine endometrium morphologically changed? Results obtained are as follows: Concentrations of serum estradiol and progesterone were significantly increased on day 4 and 5 of pregnancy. Uterine concentrations of PGE and $PGE_{2a}$ were sharply increased on day 1 and maintained similar concentrations thereafter, reaching the maximum on day 5. Both prostaglandins (PGs) concentrations were gradually decreased thereafter. Furthermore, concentrations of PGs in implant sites were greater than those in non-implant sites. PBR (pontamine blue reaction) in uterine endometrium was positive on day 6 of pregnancy, indicating that vascular permeability was increased. Edema and changes in structure of cell components were pronounced in stroma where PBR was developed. Moreover, these were more prominent in implant sites than non-implant sites. These results suggest that uterine PGs as well as steroid hormones increase during implantation in rats and these hormones might be involved in the process of implantation by modulating vascular permeability and the fine structures of uterine endometrial cells.

난소제거된 흰쥐에서 난소호르몬에 의한 LHβ subunit의 유전자 발현조절

김창미(Chang-mee Kim),박덕배(Deok-bae Park),유경자(Kyung-za Ryu) 대한약리학회 1993 대한약리학잡지 Vol.29 No.2

난소호르몬에 의하여 황체형성호르몬(luteinizing hormone; LH) subunit의 유전자 발현이 어떻게 조절되는가를 조사하기 위하여 성숙한 흰쥐에서 난소를 제거하거나 또한 난소호르몬을 재 투여한 후 α 및 LHβ subunit mRNA의 수준을 조사하여 다음과 같은 결과를 얻었다. 1. 난소를 제거한 후 시간이 경과함에 따라 혈중 LH 농도 및 뇌하수체 LH 함량이 급격히 증가하였다. 또한 난소제거 후 14일 후부터 α subunit mRNA 수준이 증가하기 시작하였으며, LHβ subunit mRNA 수준은 난소제거 후 1일부터 증가하기 시작하여 혈중 LH 농도와 같은 양상으로 증가하였다. 2. 난소제거 후 21일 경과후에 난소호르몬을 투여하였을때 난소제거로 증가된 혈중 LH 농도와 α 및 LHβ subunit mRNA 수준이 감소하였다. Estradiol을 1일간 투여하였을때 부터 혈중 LH 농도 및 α와 LHβ subunit mRNA 수준이 감소하였으며, progesterone을 4일간 처리하였을때에 혈중 LH농도가 감소하였다. 3. Estrogen 길항제인 LY117018를 estradiol과 동시에 처리하거나, progesterone 길항제인 RU 456을 progesterone과 동시에 처리하였을때 estradiol과 porgesterone에 의하여 감소되었던 혈중 LH 농도 및 α와 LHβ subunit mRNA 수준이 유의하게 회복되었다. 이상의 결과로 보아 LH 분비에 있어서 LHβ subunit mRHA 수준의 변화가 속도결정단계 (rate limiting step)인 것으로 보이며, 난소홀몬은 α 및 LHβ subunit mRNA 수준을 조절하므로써 pretranslation 단계에서 LH 생합성을 조절하는 것으로 생각된다. Pituitary LH release has been known to be regulated by the hypothalamic gonadotropin releasing hormone (GnRH) and the gonadal steroid hormones. In addition, neurotransmitters and neuropeptides are actively involved in the control of LH secretion. The alteration in LH release might reflect changes in biosynthesis and/or posttranslational processing of LH. However, little is known about the mechanism by which biosynthesis of LH subunits is regulated, especially at the level of transcription. In order to investigate if ovarian steroid hormones regulate the LH subunit gene expression, α and LHβ steady state mRNA levels were determined in anterior pituitaries of ovariectomized rats. Serum LH concentrations and pituitary LH concentrations were increased markedly with time after ovariectomy. α and LHβ subunit mRNA levels after ovariectomy were increased in a parallel manner with serum LH concentrations and pituitary LH contents, the rise in LHβ subunit mRNA levels being more prominent than the rise in α subunit mRNA. α and LHβ subunit mRNA levels in ovariectomized rats were negatively regulated by the continuous treatment of ovarian steriod hormones for 1 ~ 4 days and LHβ subunit mRNA seemed to be more sensitive to negative feedback of estradiol than progesterone. Treatment of estrogen antagonist, LY117018 or progesterone antagonist, RU486 significantly restroed LH subunit mRNA levels as well as LH release which were suppressed by estradiol or progesterone treatment. These results suggest that ovarian steroids negatively regulate the LH synthesis at the pretranslational level by modulating the steady state levels of α and LHβ subunit mRNA and LHβ subunit mRNA seemed to be more sensitive to negative feedback action of estradiol than progesterone.

흰쥐 신경계 발달에 따른 전압의존성칼슘채널 α1 subunits (α1D, α1B, α1A, α1E) 유전자들의 발현에 관한 연구

김창미(Chang-Mee Kim),한승훈(Seung Hun Han),한상준(Sang Jun Han),김동연(Dong Yeon Kim),이경상(Kyung Sang Lee),전용혁(Yong-Hyuck Chun) 대한해부학회 1998 Anatomy & Cell Biology Vol.31 No.5

전압의존성 칼슘채널 (voltage dependent calcium channel, VDCC)의 구성요소 중 칼슘이온통로로 작용하는 α1 subunit 중에서 신경계에 발현하는 것으로 알려진 α1A, α1B, α1D 및 α1E subunit의 유전자 발현양상을 출생 전 태자기와 출생 후 성장기의 흰쥐 신경계에서 in situ hybridization 조직화학법으로 관찰하였다. 성숙한 흰쥐 뇌에서 각각의 유전자는 광범위하고 특이한 발현양상을 보였다. VDCC α1A 유전자는 해마의 CA3 부위와 소 뇌에서 높게 발현하였으며, VDCC α1B 유전자는 뇌 전체에서 광범위하고 낮게 발현하였다. VDCC α1D 유전자는 후각망울의 승모세포층, 시각교차위핵, 치아이랑 등에서 높게 발현하였으며, VDCC α1E 유전자는 후각망울, 해마와 치아이랑, 안쪽고삐핵소뇌에서 높은 발현을 보였다. 태자기 각종 조직에서 VDCC α1D 유전자는 신경조직에서 뿐만 아니라 허파, 창자, 콩팥, 간, 뼈대근육 등의 비신경계조직에서도 발현이 관찰되었으나, VDCC α1A, VDCC α1B 및 VDCC α1E 유전자는 신경조직 이외의 부위에서는 거의 발현을 보이지 않는 신경조직 특이성을 보였다. 흰쥐 뇌 발달과정에서 VDCC α1A, VDCC α1D 및 VDCC α1E 유전자 발현은 14일된 태자에서 관찰되기 시작하여 출생 후 14일까지 발현부위 및 정도가 증가되었으며 그 이후 점차 감소하였다. 한편 VDCC α1B 유전자는 14일된 태자에서 발현하기 시작하여 출생 직전과 직후에 가장 높은 발현을 보였으며 그 이후 점차 감소되는 양상을 보였다. 이들 유전자들은 공통적으로 뇌실층 (ventricular layer)에 비해 외투층(mantle layer)에서 높게 발현하였다. 성숙한 흰쥐 신경계에서의 특이한 발현양상으로부터 각각의 전압의존성 칼슘채널이 고유한 역할을 하는 것을 예측할 수 있으며, 발달과정에서 신경세포의 분화가 일어나는 부위에서 높게 발현하며 분화가 왕성하게 일어나는 시기 이후에는 발현이 감소하는 양상에서 신경계 분화에 관여하는 것을 예측할 수 있다. Voltage dependent calcium channels (VDCCs) mediate Ca++ influx into cells and are responsible for regulation of a variety of physiological effects. The key functional property of VDCCs are attributed to the calcium-pore forming α1 subunit. In this study, distribution pattern of α1 subunit (α1D, α1B, α1A, α1E) mRNA of VDCCs in developing and adult rat brain was investigated by in situ hybridization histochemistry. In the adult rat brain, each α1 subunit mRNA displayed a specific and distinct distribution pattern. α1D was highly expressed in the olfactory bulb, dentate gyrus, pituitary gland, pineal gland, hypothalamus, superior colliculus and cerebellum. Relatively low level of α1B was expressed throughout the whole brain and strong expression of α1A was observed in CA3 area of Ammon's horn, medial geniculate body, inferior colliculus and cerebellum. High level of α1E was found in the olfactory bulb, hippocampus, dentate gyrus, medial habenular nucleus and cerebellum. Moreover, α1B, α1A and α1E were expressed only in the nervous system but α1D was expressed not only in the nervous system but also in other tissues including liver, heart, lung and skeletal muscle. Generally the expression of α1D, α1A, and α1E subunit was observed from E14 and thereafter the intensity of labeling was gradually increased to P14 and then decreased to the adult level. But the expression of α1B subunit was observed from E14 and gradually increased to E20 and P0 and then decresaed. From the differential expressions of VDCC α1 subunits in developing and adult rat brain, it is suggested that each type of VDCCs may play a distinct roles in neural and nonneural tissues, and the VDCCs may be related with development of nervous system.

흰쥐 뇌하수체전엽 배양세포에서 GnRH 및 난소호르몬에 의한 LHβ subunit 유전자 발현 조절에 관한 연구

김창미(Chang-mee Kim),박일선(Il Sun Park),유경자(Kyung-za Ryu) 대한약리학회 1994 대한약리학잡지 Vol.30 No.1

흰쥐의 뇌하수체 전엽배양세포에 gonadotropin-releasing hormone (GnRH)을 처리하였을 때 시간이 경과함에 따라 GnRH농도에 비례하여 luteinizing hormone(LH)의 분비가 증가하였으며, 2시간까지 급격하게 증가하였다. 또한 GnRH를 처리하였을때 α subunit mRNA의 농도는 증가하지 않았으나 LHβ subunit mRNA의 농도는 GnRH 농도에 비례하여 증가하였으며, GnRH 처리후 6시간 이후부터 유의하게 증가하였다. 특히 최종농도가 2 × 10^-10M이 되도록 GnRH를 처리하였을 때 LHβ subunit mRNA 농도가 2.7배 정도 최대로 증가하였다. 또한 estradiol을 단독으로 또는 GnRH와 동시에 처리하였을때 LH분비가 증가하지 않았으나 progesterone을 GnRH와 동시에 처리하였을때 LH분비가 유의하게 증가하였다. 또한 LHβ subunit mRNA의 농도는 estradiol및 progesterone을 단독으로 또는 GnRH와 동시에 처리하였을때 난소호르몬 농도에 의존적으로 LHβ subunit mRNA의 농도가 증가하였다. Estradiol에 의한 LHβ subunit mRNA의 증가양상은 estrogen 길항제인 LY117018에 의하여 유의하게 감소하였다. 이러한 결과로 보아 GnRH는 steady state LHβ subunit mRNA 농도에 영향을 미치므로써 LH분비 및 LH subunit 생합성을 조절하며 난소호르몬은 뇌하수체에 직접 작용하여 LH분비 및 LH subunit 생합성에 영향을 주는 것으로 보인다. The effects of gonadoropin-releasing hormone (GnRH) and ovarian steroid hormones on the release of luteinizing hormone (LH) and its subunit mRNA levels were investigated in anterior pituitary cells in culture. LH concentration was measured by a specific radioimmunoassay and mRNA levels of u and LHβ subunits by RNA slot blot hybridization assay. GnRH stimulated LH release in a dose-dependent manner from cultured pituitary cells. However, the basal LH release in the absence of GnRH was not changed during the course of 24h culture, strongly suggesting that release of LH is directly controlled by GnRH. The treatment of the pituitary cells with GnRH increased LHβ subunit mRNA levels in a dose-dependent manner, reaching the maximum with 2 × 10^-10M GnRH while no significant increase in α subunit mRNA levels was observed after GnRH treatment. Estradiol did not augment GnRH-induced LH release while progesterone augmented GnRH-induced LH release in a dose-dependent manner at the level of pituitary. However, estradiol and progesterone increased basal and GnRH-induced LHβ subunit mRNA levels in a dose-dependent manner. The treatment of estrogen antagonist, LYI17018 blocked the effect of estradiol on GnRH-induced LHβ subunit mRNA levels in a dose-dependent manner while progesterone antagonist, Ru486 tended to block the effect of progesterone on GnRH-induced LHβ subunit mRNA levels. It is therefore suggested that GnRH Playa a major role in LH release and subunit biosynthesis by influencing the steady state LHβ subunit mRNA loves and ovarian steroid hormones modulate subunit biosynthesis via directly acting on pituitary gonadotropes.

Modulation of Uterine Phospholipase $A_2$ Activity by Estradiol During the Delayed Implantation Process in Rats

윤미정,김창미,최임순,유경자,Yoon, Mi-Chung,Kim, Chang-Mee,Choe, Rim-Soon,Ryu, Kyung-Za The Korean Society of Pharmacology 1991 대한약리학잡지 Vol.27 No.2

The present study was performed to determine whether estradiol, via cAMP mediation, induces prostaglandin synthesis by modulating phospholipase $A_2$ activity which hydrolyzes phospholipids into arachidonic acids, a precursor for prostaglandin synthesis, during the implantation process in rats. Uterine phospholipase $A_2$ activity was elevated on day 5 of pregnancy when implantation normally occurs in rats. Moreover, phospholipase $A_2$ activity was higher in the implant sites than in the non-implant sites of uterus on day 6. In delayed implantation model, phospholipase $A_2$ activity was increased at 12 hrs after estradiol administration and at 8 hrs after dbcAMP administration. In addition, higher activity of phospholipase $A_2$ was induced by the treatment of estradiol plus theophylline, compared with estradiol-only treated group. The simultaneous treatment of indomethacin with estradiol or dbcAMP did not alter phospholipase $A_2$ activity compared with estradiol or dbcAMP-only treated group although significant suppression was observed in uterine PGE and $PGF_{2{\alpha}}$ concentrations. These results suggest that estradiol or cAMP stimulates uterine phospholipase $A_2$ activity, thereby increasing prostaglandin synthesis during the implantation process in rats.

Effects of Extracellular $Ca^{++}$ on PKC or cAMP-stimulated Increases in LH Release and $LH{\beta}$ Subunit mRNA Levels in Rat Anterior Pituitary Cells

박덕배,김창미,천민석,유경자,Park, Deok-Bae,Kim, Chang-Mee,Cheon, Min-Seok,Ryu, Kyung-Za The Korean Society of Pharmacology 1996 대한약리학잡지 Vol.32 No.3

We examined the effects of EGTA and verapamil on phorbol ester-and forskolin-stimulated LH releases and $LH{\beta}$ subunit mRNA levels in order to verify the role of extracellular $Ca^{++}$ on PKC- or cAMP-induced increases in LH release and $LH{\beta}$ subunit mRNA levels in cultured anterior pituitary cells of rat. Forskolin-stimulated $LH{\beta}$ subunit mRNA levels as well as LH release were all suppressed by prevention of $Ca^{++}$ mobilization from extracellular environment, after the treatment of EGTA as a $Ca^{++}$ chelator or verapamil as a $Ca^{++}$ channel blocker. PMA-stimulated $LH{\beta}$ subunit mRNA levels were also suppressed by the treatment of EGTA and verapamil, while PMA-induced LH release was not affected. From the present study, it is, therefore, suggested that PKC activation and cAMP elevation all stimulate $LH{\beta}$ subunit mRNA levels and these are extracellular $Ca^{++}$-dependent. However, LH releases by PKC activation and cAMP increase seem to be different each other. LH release by PKC activation is thought to be independent of extracellular $Ca^{++}$. On the other hand, cAMP stimulated-LH release is thought to be dependent on the entry of extracellular $Ca^{++}$.

cAMP Mediation in Estradiol-induced Uterine Prostaglandin Synthesis During the Delayed Implantation Process in Rats

윤미정,김창미,최임순,유경자,Yoon, Mi-Chung,Kim, Chang-Mee,Choe, Rim-Soon,Ryu, Kyung-Za The Korean Society of Pharmacology 1991 대한약리학잡지 Vol.27 No.2

본 연구에서는 흰쥐의 착상지연을 유도하여 착상기간동안 자궁조직내 prostaglandin (PG) 생합성이 어떠한 인자에 의해서 조절되는가를 관찰하여 다음과 같은 결과를 얻었다. 흰쥐의 착상지연과정동안 estradiol을 처리하면 처리후 4시간만에 자궁조직내의 cAMP의 농도가 급격하게 증가하였다. PGE와 $PGF_2{\alpha}$의 농도는 estradiol을 처리한 후 12시간이 경과하였을때 증가하였으나 $PGF_2{\alpha}$의 증가는 통계적으로 유의하지는 않았다. 또한 indomethacin을 estradiol과 동시에 처리하면 estradiol 처리로 인한 PGE와 $PGF_2{\alpha}$의 농도 증가는 나타나지 않았으나 cAMP 농도는 증가하였다. dbcAMP를 처리하면 자궁내 PGE 및 $PGF_2{\alpha}$의 농도가 증가하기 시작하여 estradiol이 투여시에 비하여 4시간 빨리 8시간후에 최고치에 도달하였으며 phosphodiesterase inhibitor인 theophylline을 전처치하면 estradiol만 투여한 것에 비하여 자궁조직내 PGE 및 $PGF_2{\alpha}$의 농도가 유의하게 증가하였다. 이상의 결과로 보아 흰쥐의 착상지연과정동안 estradiol이 자궁의 prostaglandin 합성을 증가시키며 이러한 증가는 cAMP의 증가를 매개하는 것으로 생각된다.

Action Mechanism of Antiestrogens on Uterine Growth in Immature Rats

이중빈,윤미정,김창미,홍사석,유경자,Lee, Jung-Bin,Yoon, Mi-Chung,Kim, Chang-Mee,Hong, Sa-Suk,Ryu, Kyung-Za The Korean Society of Pharmacology 1990 대한약리학잡지 Vol.26 No.2

비스테로이드성 항에스트로젠제는 표적기관에서 estrogen 수용체와 상경적으로 결합하므로써 estrogen의 작용을 억제하는 것으로 알려져 있다. 비스테로이드성 항에스트로젠제는 대체로 triphenylethylene계로서 tamoxifen, clomiphene, LYl17018등이 있으며 표적기관에서 estrogen의 작용을 억제하기 때문에 estrogen과 관련된 질환을 치료하는데 이용되어 오고 있다. 본 연구에서는 생후 21-23일된 미성숙 흰쥐를 재료로 항에스트로젠제중 tamoxifen과 LY117018이 자궁세포 성장에 어떠한 영향을 미치며 어떠한 기전으로 estrogen의 작용을 길항하는지를 규명하고자, 항에스트로젠제가 estrogen작용의 중요 지포에 미치는 영향을 비교 관찰하여 다음과 같은 결과를 얻었다. Tamoxifen과 LY117018은 자궁세포에서 estrogen의 영향이 없는 경우에는 estrogen agonist로, estrogen작용하에서는 estrogen antagonist로서 작용하였다. Estrogen 작용의 여러 가지 지표에 대해 tamoxifen이 LY117018보다 agonistic effect는 더 컸으나, antagonistic effect는 LY117018이 더 큰 것으로 나타났다. Estrogen 수용체에 대한 결합능은 LY117018이 estradiol보다는 약간 낮았으나 용량에 비례하여 estrogen 수용체와 결합하였다. 그러나 tamoxifen은 estrogen 수용체에 대한 결합이 아주 낮았다. Estrogen 수용체에 대한 binding affinity는 estradiol(100%), LY117018(77%), tamoxifen(6.3%) 순으로 나타났다. 항에스트로젠제의 생체내 투여는 estrogen 존재 유무에 따라 estrogen 수용체 농도에 agonist 또는 antagonist로 작용하였다. 항에스트로젠제의 단독투여는 progesterone 수용체 생성을 증가시키나, estrogen에 의하여 유도된 progesterone 수용체 생성을 억제하였다. 이상의 결과로 보아, tamoxifen과 LY117018은 estrogen유무에 따라 흰쥐 자궁세포에서 estrogen antagonist로서 뿐만 아니라 agonist로서도 작용함을 알 수 있다. 그러나 estrogen수용체와의 결합능력이 아주 낮은 tamoxifen은, 용량에 비례하여 estrogen수용체에 결합하므로써 작용하는 LY117018과는 다른 기전으로 작용하는 것으로 생각된다. In the present study, we examined the effects of tamoxifen and LY117018 on various parameters for the estrogenic actions in order to understand the mechanism by which tamoxifen and LY117018 act on the uterine cells in 21-23 day old immature rats. Tamoxifen and LY117018 stimulated uterine weight and uterine contents of DNA, protein, and peroxidase activity in the absence of estradiol while inhibited above parameters in the presence of estradiol. Both cytosolic and nuclear progesterone receptors were increased by the treatment of tamoxifen and LY117018 as well as estradiol, but estradiol-induced increase in the progesterone receptors were reduced by the treatment of antiestrogens. These effects were enhanced by the multiple injections of antiestrogens. It seemed that tamoxifen was more agonistic than LY117018 but less antagonistic than LY117018, judged by their effects on various parameters for the estrogenic action. The affinities of estradiol, tamoxifen, and LY117018 for the estrogen receptor were $0.17{\pm}0.01nM(100%)$, $1.10{\pm}0.01nM(6.3%)$, and $0.23{\pm}0.01nM(77%)$, respectively. Furthermore, LY117018 was the competitive ligand for the estrogen receptor in dose-related manner but tamoxifen was not. Following estradiol treatment, nuclear estrogen receptor was sharply increased by 1 h, reaching the maximum by 16 h, while tamoxifen and LY117018 slightly increased nuclear estrogen receptor by 1 h and then decreased thereafter. It is therefore concluded that LY117018 is a competitive antagonist for the estrogen receptor with less estrogenic activity, compared to tamoxifen with low affinity to the estrogen receptor, and tamoxifen may act through other binding site than the estrogen receptor.