• Title/Summary/Keyword: Granulosa cells

Search Result 239, Processing Time 0.028 seconds

Fibrinogen mRNA Expression Up-Regulated in Follicular Cyst of Korean Cattle (한우 난포낭종에서 증가되는 섬유소원 유전자 발현)

  • Tak, Hyun-Min;Han, Jae-Hee;Kang, Da-Won
    • Journal of Embryo Transfer
    • /
    • v.25 no.1
    • /
    • pp.29-34
    • /
    • 2010
  • Follicular cystic ovary (FCO) is one of the major causes of reproductive failure in cattle. Genetic alterations affect the function of diverse cells and/or tissues, which could be present in cystic ovaries. A microarray analysis was performed to screen differential gene expressions in follicular cystic follicles of cattle. In this study, we hypothesized that follicular cysts may be induced by changes in ion- and transporter-related gene expression. Microarray data showed that fibrinogen-gamma (FGG) and low density lipoprotein receptor-related protein 8 (LRP8) were up-regulated, while choline transporter-like protein 4 (SLC44A4), very long-chain acyl-CoA synthetase homolog 2 (SLC27A5), annexin 8 (ANXA8), and aquaporin 4 were down-regulated in follicular cystic follicles. A semi-quantitative RT-PCR was carried out to validate DEGs altered in follicular cystic follicles. Of six DEGs, three DEGs (FGG, SLC44A4, and aquaporin 4) showed a positive correlation between microarray and semi-quantitative PCR data. We focused on FGG, among three DEGs, which was highly up-regulated in follicular cystic follicles. The FGG mRNA was upregulated by 8.4-fold and by 1.7-fold in the bovine follicular cystic follicles as judged by microarray and RT-PCR analysis, respectively. However, there was no significant changes in the expression level of FGG protein in both follicular cystic follicles and granulosa cells isolated from follicular cystic follicles by Western blot analysis. Although this study does not reveal a positive correlation between the mRNA and protein level, FGG appears to be an important biomarker in the discrimination of follicular cyst from normal ovary.

Subcutaneous Administration of Highly Purified-FSH(HP-FSH) versus Intramuscular Administration of FSH in Superovulation for IVF-ET (체외수정시술을 위한 과배란유도시 Highly Purified Follicle Stimulating Hormone (HP-FSH) 피하주사와 Follicle Stimulating Hormone 근육주사의 비교연구)

  • Bai, S.W.;Kim, J.Y.;Won, J.G.;Jung, C.J.;Chang, K.H.;Lee, B.S.;Park, K.H.;Cho, D.J.;Song, C.H.
    • Clinical and Experimental Reproductive Medicine
    • /
    • v.24 no.1
    • /
    • pp.135-141
    • /
    • 1997
  • The early studies demonstrated that the relative amount of FSH was important for stimulating normal ovarian activity and demonstrated the existence of a threshold level for FSH, above which follicular growth was activated. It was found that only a modest increase in circulating FSH level above the threshold (between 10 and 30%) was required to stimulate folliculogenesis. In addition, FSH is primary responsible for initiating estradiol production through the activation of the aromatase enzyme system in granulosa cells, follicular secretion and growth. LH on the other hand, plays a supportive role in ovarian steroidogenesis, stimulating the ovarian thecal cells to produce androgen, the precursor for estradiol synthesis. But there is now an increasing number of reports in the literature demonstrating an adverse effect of LH on fertility and miscarriage in infertile and fertile women. So HP-FSH is the drug of a highly purified FSH preparation which has a higher specific activity and far fewer impurities than FSH. This study was performed to evaluate the efficacy and safety of HP-FSH administered (SC; subcutaneous) versus FSH(IM; intramuscular) for ovulation induction. 20 candidates patients for ovulation induction were participated. All patients underwent pituitary desensitizing with a long gonadotropin-releasing hormone (GnRH) agonist protocol and ovulation induction was started with HP-FSH SC (10 patients; group I) or FSH IM (10 patients; group II). After ovulation, outcome of ovulation induction and local reaction of injection site were compared. There were no difference of outcome of ovulation in two groups except pregnancy rate/embryo transfer. Group I had a higher pregnancy rate/ embryo transfer than Group II (44.4% Vs 28.6%). Pain, redness, tenderness, bruising and itching when the injection received on the first 5 days of treated (50 SC and 50 IM injections) were assessed. There were no significant difference (P>0.05) in the incidence of tenderness, bruising and itching between the IM and SC injection. But IM injection (FSH) had a tendency of higher above incidence. The number of reports of pain, redness were significantly increased in IM injection group (P<0.05). These results indicate that SC administration of HP-FSH has been shown to be as effect for superovulation as traditional gonadotropins, with an improved safety profile due to the removal of extaneous proteins.

  • PDF

Gelatinases of Extracellular Matrix of Human Oocyte-Cumulus Complex (사람 난자-난구 복합체 ECM의 Gelatinase)

  • 이인선;나경아;김해권
    • Development and Reproduction
    • /
    • v.5 no.2
    • /
    • pp.123-129
    • /
    • 2001
  • When mammalian oocytes undergo maturation, cumulus cells surrounding the oocyte exhibit remodeling of their structure known as cumulus expansion. Many molecules including hyaluronic acid participate in this remodeling. The present study aimed to investigate a possible existence of matrix metalloproteinases(MMPs) in the extracellular matrix(ECM) of human oocyte-cumulus complex. ECM was extracted from the human oocyte-cumulus complex. Gelatin gel zymogram of ECM exhibited 7 gelatinases having molecular weight of 300kDa, 240kDa, 200kDa, 180kDa, 116kDa, 97kDa, and 84kDa. This gelatinase profile was very different from that of ovarian mural granulosa cell extract or white blood cell extract, indicating that the oocyte-cumulus complex donating ECM was free from other than cumulus cells. When ethylenediaminetetraacetic acid or 1', 10'-phenanthroline was added to the reaction buffer during zymographic development, almost gelatinase activities were abolished, suggesting that they were MMPs. Following incubation of ECM in the presence of aminophenylmercuric acetate, an activator of proMMPs, 4 gelatinases of 240kDa, 180kDa, 97kDa, and 84kDa disappeared with the concomitant appearance of 80kDa, 65kDa, and 60kDa gelatinases. Based upon these observation, it is suggested that ECM of the human oocyte-cumulus complex consists of gelatinases, presumed to be MMP-2 and MMP-9 isoforms.

  • PDF

Protective Effect of BOEC Co-Culture System against Nitric Oxide on Development of Bovine IVM/IVF Embryos

  • Jang, Hyun-Yong;Jung, Yu-Sung;Li, Zheng-Yi;Yoon, Hyoung-Jong;Cheong, Hee-Tae;Kim, Jong-Taek;Park, Choon-Keun;Yang, Boo-Keun
    • Reproductive and Developmental Biology
    • /
    • v.32 no.3
    • /
    • pp.167-173
    • /
    • 2008
  • Somatic cells such as oviduct epithelial cell, uterine epithelial cell, cumulus-granulosa cell and buffalo rat river cell has been used to establish an effective culture system for bovine embryos produced in in vitro. But nitric oxide (NO) metabolites secreted from somatic cells were largely arrested the development of bovine in vitro matured/ in vitro fertilized (IVM/IVF) embryos, suggesting that NO was induced the embryonic toxic substance into culture medium. The objective of this study was to investigate whether BOEC co-culture system can ameliorate the NO-mediated oxidative stress in the culture of bovine IVM/IVF embryos. Therefore, we evaluated the developmental rate of bovine IVM/IVF embryos under BOEC co-culture system in the presence or absence of sodium nitroprusside (SNP), as a NO donor, and also detected the expression of growth factor (TGF-$\beta$, EGF and IGFBP) and apoptosis (Caspase-3, Bax and Bcl-2) genes. The supplement of SNP over 5 uM was strongly inhibited blastocyst development of bovine IVM/IVF embryos than in control and 1 uM SNP group (Table 2). The developmental rates beyond morulae stages of bovine IVM/IVF embryos co-cultured with BOEC regardless of SNP supplement (40.4% in 5 uM SNP+ BOEC group and 65.1% in BOEC group) were significantly increased than those of control (35.0%) and SNP single treatment group (23.3%, p<0.05: Table 3). The transcripts of Bax and Caspase-3 genes were detected in all experiment groups (1:Isolated fresh cell (IFC), 2:Primary culture cell (PCC), 3:PCC after using the embryo culture, 4: PCC containing 5 uM SNP and 5: PCC containing 5 uM SNP after using the embryo culture), but Bcl-2 gene was not detected in IFC and PCC (Fig. 1). In the expression of growth factor genes, TGF-$\beta$ gene was found in all experimental groups, and EGF and IGFBP genes were not found in IFC and PCC (Fig. 2). These results indicate that BOEC co-culture system can increase the development beyond morula stages of bovine IVM/IVF embryos, possibly suggesting the alleviation of embryonic toxic substance like nitric oxide.

Effects of Jeongkyeong-Tang on the Estradiol Valerate-induced Polycystic Ovary in Rats (정경탕(定經湯)이 Estradiol Valerate로 유도된 흰쥐의 다낭성 난소에 미치는 영향)

  • Nam, Eun-Jung;Lee, Dong-Nyung;Seo, Il-Bock;Kim, Hyung-Jun
    • The Journal of Korean Obstetrics and Gynecology
    • /
    • v.20 no.1
    • /
    • pp.99-113
    • /
    • 2007
  • Purpose : This study was designed to investigate the effects of Jeongkyeong-Tang(JKT) on the polycystic ovary(PCO) induced by estradiol valerate(EV) in rats. Methods : PCO was induced by single intramuscular injection with EV(4mg) in female rats. Normal group(n=8) were injected with sesame oil and orally administrated distilled water for sixty days. PCO control group(n=8) were injected with EV and orally administrated distilled water for sixty days. JKT treated group(n=8) were injected with EV and orally administrated JKT for sixty days. Then we measured weights of body, ovaries and adrenal glands, and measured content of serum estrogen. The histomorphometrical changes of ovaries were also evaluated. The expressions of nerve growth factor(NGF) were analyzed in the central nervous system, adrenal glands and ovaries by immunohistochemistry. Results : - The weights(mg) of ovaries in JKT treated group (69.7${\pm}$6.7) were significantly increased( p<0.001) compared with PCO control group(46.7${\pm}$12.2). - The numbers of secondary follicles in JKT treated group(4.00${\pm}$l.31) were significantly increased(p <0.05) compared with PCO control group(2.25${\pm}$1.39). - The numbers of mature follicles in JKT treated group(5.50${\pm}$1.51) were significantly increased(p<0.01) compared with PCO control group(2.88${\pm}$1.13). - The numbers of atretic follicles in JKT treated group(2.75${\pm}$l.16) were significantly decreased(p<0.001) compared with PCO control group(6.88${\pm}$2.03). - The numbers of corpora lutea in JKT treated group(4.13${\pm}$1.46) were significantly increased(p<0.01) compared with PCO control group(2.13${\pm}$1.46). - The contents(pg/ml) of serum estrogen in JKT treated group(115.18${\pm}$18.29) were significantly decreased(P<0.01) compared with PCO control group(153.06${\pm}$29.47). - The expressions of NGF-immunoreactive cells in the ovarian granulosa cells in JKT treated group were lesser observed than PCO control group. Conclusion : From the above results, we concluded that Jeongkyeong-Tang has inhibitory effect on the development of EV-induced polycystic ovary. And it's effect may be related with decreased NGF activities in the ovary.

  • PDF

Effect of Equilibration Time and Cell Stage on the Survival of IVF Bovine Embryos Cryopreserved by Vitrification (한우 체외수정란의 동결보존시 평형시간과 배 발달단계가 생존성에 미치는 영향)

  • 공일근;주영국;이은봉;김용권;박충생
    • Journal of Embryo Transfer
    • /
    • v.9 no.1
    • /
    • pp.7-14
    • /
    • 1994
  • The present experiments on cryopreservation were designed to examine the effects of solution toxicity, equilibration time and cell stages on the post-thaw survival of bovine IVF embryos. The oocytes were matured in vitro(IVM) for 24 hrs. in TCM-199 supplemented with 35 $\mu$g /ml FSH, 10 $\mu$g /ml LH, 1 $\mu$g /ml estradiol-17$\beta$ and granulosa cells at 39$^{\circ}C$ under 5% $CO_2$ in air. They were fertilized in vitro(IVF) by epididymal spermatozoa treated with heparin for 24 hrs., and then the zygotes were co-cultured in vitro(IVC) with bovine oviductal epithelial cells for 7 to 9 days. The bovine IVF embryos were exposed to the EFS solution in one step at room temperature, kept in the EFS solution during different period for toxicity test, vitrified in liquid nitrogen, and thawed rapidly. 1. after the bovine blastocysts were exposed to EFS solution for 2 min. at room temperature and then they were washed in 0.5 M sucrose solution and TCM-199, they were cultured to examined cryoprotectant induced injury during exposure, Most of the embryos(95.0%) developed to reexpanded blastocoels. However, when the exposure time was extended to 5 and 10 min, these development rates dropped dramatically in 5 min. (69.5%) and 10 min. (47.4%), respectively, 2. When the bovine IVF embryos were vitrified in EFS solution after the equilibration for 1 and 2 min. exposure, The embryos to have reexpanded blastocoels following thawing, washing and culture processes were found to he 82.6 and 73.9%, respectively. However, when the exposure time was extended to 3 min, this survival rate dropped to 18.2%. The optimal time for equilibration of bovine IVF blastocysts in EFS solution seemed to he 1~2 min. 3. When the bovine IVF embryos were equilibrated for 1 min. the significantly (P<0. 05) higher post-thaw survival rates were obtained from the embryos of blastocyst stage(81.3%) than morulae stage(5. 1%). The optimal cell stage for viterification with EFS solution proven to he blastocyst stage in bovine IVF embryos. 4. The number of blastomeres of blastocyst stage was examined with nuclear staining with Hoechst 33342 during 7 to 9 days post-insemination. The cell counts of frozen bovine IVF embryos were found significantly(P$\geq$7.5 and those of the fresh embryos 76.6$\geq$7. 1, which were cultured in the sarne period and conditions as frozen embryos.

  • PDF

Effects of Gwibi-Tang on the Estradiol Valerate-induced Polycystic Ovaries in Rats (귀비탕(歸脾湯)이 Estradiol Valerate로 유도된 흰쥐의 다낭성 난소에 미치는 영향)

  • Lee, Yeon-Kyeong;Seo, Il-Bock;Lee, Dong-Nyung;Kim, Hyung-Jun
    • The Journal of Korean Obstetrics and Gynecology
    • /
    • v.21 no.3
    • /
    • pp.60-74
    • /
    • 2008
  • Purpose: This study was designed to investigate the effects of Gwibi-Tang(GBT) on the polycystic ovary(PCO) induced by estradiol valerate(EV) in rats. Methods: PCO was induced by single intramuscular injection with EV(4mg) in female rats. Normal group(n=8) were injected with sesame oil and orally administrated distilled water for eight weeks. PCO control group(n=8) were injected with EV and orally administrated distilled water for eight weeks. GBT treated group(n=8) were injected with EV and orally administrated GBT for eight weeks. Then we measured weight of body, ovaries, adrenal glands, and uterus of rats. The histopathology changes of ovaries were also evaluated. The expression of nerve growth factor(NGF) was analyzed in the central nervous system, adrenal glands and ovaries by immunohistochemistry. And also CRF expression in median eminance of Rats were analyzed. Results: 1. The weight(g) of rats in GBT treated group($275{\pm}14$) was significantly increased(p<0.01) compared with control group($253{\pm}8$), 2. The weight(mg) of ovaries in GBT treated group($75.8{\pm}16.7$) was significantly increased(p<0.001) compared with control group($37.4{\pm}6.7$). 3. The number of mature follicles in GBT treated group($3.6{\pm}1.2$) was significantly increased(p<0.01) compared with control group($1.5{\pm}1.5$. 4. The number of atretic follicles in GBT treated group($8.0{\pm}3.1$) was significantly decreased(p<0.01) compared with control group($18.6{\pm}6.0$). 5. The number of cystic follicles in GBT treated group($0.5{\pm}0.5$) was significantly increased(p<0.01) compared with control group($2.3{\pm}1.3$). 6. The number of corpora lutea in GBT treated group($6.1{\pm}3.9$) was significantly increased(p<0.01) compared with control group($1.6{\pm}2.3$). 7. The expression of NGF-immunoreactive cells in the ovarian granulosa cells in GBT treated group was lesser observed than control group. Conclusion: From the above results, we concluded that Gwibi-Tang has inhibitory effect on the development of EV-induced polycystic ovary. And it's effect may be related with decreased NGF activities in the ovary.

  • PDF

Expression of Nesfatin-1/NUCB2 and Its Binding Site in Mouse Ovary (생쥐 난소 내 Nesfatin-1/NUCB2 발현과 결합 부위 확인)

  • Kim, Jin-Hee;Youn, Mi-Ra;Bang, So-Young;Sim, Ji-Yeon;Kang, Hee-Rae;Yang, Hyun-Won
    • Development and Reproduction
    • /
    • v.14 no.4
    • /
    • pp.287-295
    • /
    • 2010
  • It was recently reported that nesfatin-1/NUCB2, which is secreted from the brain, controls appetite and energy metabolism. The purpose of this research was to confirm whether or not the protein and its binding site should have been expressed in the mouse reproductive organs and to know the possible effects of nesfatin-1 on the reproductive function. Using the ICR female mouse ovary and uterus, the expression of NUCB2 mRNA was confirmed with the conventional PCR and the relative amount of NUCB2 mRNA in the tissues was analyzed with real-time PCR. Immunohistochemical staining was performed using the nesfatin-1 antibody to investigate the nesfatin-1 protein expression and the biotin conjugated nesfatin-1 to confirm the binding site for nesfatin-1 in the ovary. Furthermore, in order to examine if the expression of NUCB2 mRNA in the ovary and uterus is affected by gonadotropin, its mRNA expression was analyzed after PMSG administration into mice. As a result, the expression level of NUCB2 mRNA in the ovary and the uterus was as much as the expression level in hypothalamus. As a result of the immunohistochemical staining, nesfatin-1 proteins were localized at the theca cells, the interstitial cells, and some of the luteal cells. However, the granulosa cells in the follicles did not stain. Interestingly, the oocytes in the some follicles were stained with nesfatin-1. On the other hand, nesfatin-1 protein binding sites were displayed at the theca cells and the interstitial cells near the tunica albuginea. After PMSG administration the expression level of NUCB2 mRNA was increased in the ovary and the uterus. These results demonstrate that for the first time the nesfatin-1 and its binding site were expressed in the ovary and NUCB2 mRNA expression was controlled by gonadotropin, suggesting an important role in the reproductive organs as a local regulator. Therefore, further study is needed to elucidate the functions of nesfatin-1 on the reproductive organs.

Biological Functions of N- and O-linked Oligosaccharides of Equine Chorionic Gonadotropin and Lutropin/Chorionicgonadotropin Receptor

  • Min, K. S.
    • Proceedings of the KSAR Conference
    • /
    • 2000.10a
    • /
    • pp.10-12
    • /
    • 2000
  • Members of the glycoprotein family, which includes CG, LH, FSH and TSH, comprise two noncovalently linked $\alpha$- and $\beta$-subunits. Equine chorionic gonadotropin (eCG), known as PMSG, has a number of interesting and unique characteristics since it appears to be a single molecule that possesses both LH- and FSH-like activities in other species than the horse. This dual activity of eCG in heterologous species is of fundamental interest to the study of the structure-function relationships of gonadotropins and their receptors. CG and LH $\beta$ genes are different in primates. In horse, however, a single gene encodes both eCG and eLH $\beta$-subunits. The subunit mRNA levels seem to be independently regulated and their imbalance may account for differences in the quantities of $\alpha$ - and $\beta$ -subunits in the placenta and pituitary. The dual activities of eCG could be separated by removal of the N-linked oligosaccharide on the $\alpha$-subunit Asn 56 or CTP-associated O-linked oligosaccharides. The tethered-eCG was. efficiently secreted and showed similar LH-like activity to the dimeric eCG. Interestingly, the FSH-like activity of the tethered-eCG was increased markedly in comparison with the native and wild type eCG. These results also suggest that this molecular can implay particular models of FSH-like activity not LH-like activity in the eCG/indicate that the constructs of tethered molecule will be useful in the study of mutants that affect subunit association and/or secretion. A single-chain analog can also be constructed to include additional hormone-specific bioactive generating potentially efficacious compounds that have only FSH-like activity. The LH/CG receptor (LH/CGR), a membrane glycoprotein that is present on testicular Leydig cells and ovarian theca, granulosa, luteal, and interstitial cells, plays a pivotal role in the regulation of gonadal development and function in males as well as in nonpregnant and pregnant females. The LH/CGR is a member of the family of G protein-coupled receptors and its structure is predicted to consist of a large extracellular domain connected to a bundle of seven membrane-spanning a-helices. The LH/CGR phosphorylation can be induced with a phorbol ester, but not with a calcium ionophore. The truncated form of LHR also was down-regulated normally in response to hCG stimulation. In contrast, the cell lines expressing LHR-t63I or LHR-628, the two phosphorylation-negative receptor mutant, showed a delay in the early phase of hCG-induced desensitization, a complete loss of PMA-induced desensitization, and an increase in the rate of hCG-induced receptor down-regulation. These results clearly show that residues 632-653 in the C-terminal tail of the LHR are involved in PMA-induced desensitization, hCG-induced desensitization, and hCG-induced down-regulation. Recently, constitutively activating mutations of the receptor have been identified that are associated with familial male-precocious puberty. Cells expressing LHR-D556Y bind hCG with normal affinity, exhibit a 25-fold increase in basal cAMP and respond to hCG with a normal increase in cAMP accumulation. This mutation enhances the internalization of the free and agonist-occupied receptors ~2- and ~17-fold, respectively. We conclude that the state of activation of the LHR can modulate its basal and/or agonist-stimulated internalization. Since the internalization of hCG is involved in the termination of hCG actions, we suggest that the lack of responsiveness detected in cells expressing LHR-L435R is due to the fast rate of internalization of the bound hCG. This statement is supported by the finding that hCG responsiveness is restored when the cells are lysed and signal transduction is measured in a subcellular fraction (membranes) that cannot internalize the bound hormone.

  • PDF

Biological Functions of N- and O-linked Oligosaccharides of Equine Chorionic Gonadotropin and Lutropin/Chorionic Gonadotropin Receptor

  • Min, K.S.
    • Korean Journal of Animal Reproduction
    • /
    • v.24 no.4
    • /
    • pp.357-364
    • /
    • 2000
  • Members of the glycoprotein family, which includes CG, LH, FSH and TSH, comprise two noncovalently linked $\alpha$- and $\beta$-subunits. Equine chorionic gonadotropin (eCG), known as PMSG, has a number of interesting and unique characteristics since it appears to be a single molecule that possesses both LH- and FSH-like activities in other species than the horse. This dual activity of eCG in heterologous species is of fundamental interest to the study of the structure-function relationships of gonadotropins and their receptors. CG and LH $\beta$ genes are different in primates. In horse, however, a single gene encodes both eCG and eLH $\beta$ -subunits. The subunit mRNA levels seem to be independently regulated and their imbalance may account for differences in the quantities of $\alpha$ - and $\beta$-subunits in the placenta and pituitary. The dual activities of eCG could be separated by removal of the N-linked oligosaccharide on the $\alpha$-subunit Asn 56 or CTP-associated O-linked oligosaccharides. The tethered-eCG was efficiently secreted and showed similar LH-like activity to the dimeric eCG. Interestingly, the FSH-like activity of the tethered-eCG was increased markedly in comparison with the native and wild type eCG. These results also suggest that this molecular can implay particular models of FSH-like activity not LH-like activity in the eCG/indicate that the constructs of tethered molecule will be useful in the study of mutants that affect subunit association and/or secretion. A single-chain analog can also be constructed to include additional hormone-specific bioactive generating potentially efficacious compounds that have only FSH-like activity. The LH/CG receptor (LH/CGR), a membrane glycoprotein that is present on testicular Leydig cells and ovarian theca, granulosa, luteal, and interstitial cells, plays a pivotal role in the regulation of gonadal development and function in males as well as in nonpregnant and pregnant females. The LH/CGR is a member of the family of G protein-coupled receptors and its structure is predicted to of a large extracellular domain connected to a bundle of seven membrane-spanning a-helices. The LH/CGR phosphorylation can be induced with a phorbol ester, but not with a calcium ionophore. The truncated form of LHR also was down-regulated normally in response to hCG stimulation. In contrast, the cell lines expressing LHR-t631 or LHR-628, the two phosphorylation-negative receptor mutant, showed a delay in the early phase of hCG-induced desensitization, a complete loss of PMA-induced desensitization, and an increase in the rate of hCG-induced receptor down-regulation. These results clearly show that residues 632~653 in the C-terminal tail of the LHR are involved in PMA-induced desensitization, hCG-induced desensitization, and hCG-induced down-regulation. Recently, constitutively activating mutations of the receptor have been identified that are associated with familial male-precocious puberty. Cells expressing LHR-D556Y bind hCG with normal affinity, exhibit a 25-fold increase in basal cAMP and respond to hCG with a normal increase in cAMP accumulation. This mutation enhances the internalization of the free and agoinst-occupied receptors ~2- and ~17- fold, respectively. We conclude that the state of activation of the LHR can modulate its basal and/or agonist-stimulated internalization. Since the internalization of hCG is involved in the termination of hCG actions, we suggest that the lack of responsiveness detected in cells expressing LHR-L435R is due to the fast rate of internalization of the bound hCG. This statement is supported by the finding that hCG responsiveness is restored when the cells are lysed and signal transduction is measured in a subcellular fraction (membranes) that cannot internalize the bound hormone.

  • PDF