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    The Stimulation of Luteinizing Hormone Secretion from Anterior Pituitary Cells in Culture by Substance P: A Dissertation

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    Authors
    Shamgochian, Maureen
    Faculty Advisor
    H. Maurice Goodman
    Academic Program
    Cell Biology
    UMass Chan Affiliations
    Microbiology and Physiological Systems
    Document Type
    Doctoral Dissertation
    Publication Date
    1990-05-01
    Keywords
    Pituitary Gland
    Anterior
    Luteinizing Hormone
    Substance P
    Amino Acids, Peptides, and Proteins
    Animal Experimentation and Research
    Biological Factors
    Cells
    Endocrine System
    Hormones, Hormone Substitutes, and Hormone Antagonists
    Nervous System
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    Abstract
    The observations that substance P (SP) is localized in the anterior pituitary gland (AP) and is regulated by the hormonal status of the animal, as well as the demonstration of SP binding sites in the AP, have led to the idea that SP may participate in the regulation of AP function. Numerous and sometimes contradictory reports of SP effects on AP hormone secretion, particularly on luteinizing hormone (LH), left the question of whether SP acts directly at the level of the AP to regulate LH secretion still unanswered. To investigate a possible physiological function of SP in the AP, the effects of exogenous SP on LH secretion from AP cells from adult and prepubertal male and female rats in short term culture were studied. It was found that SP (100nM-1μM) significantly stimulates LH release in cultured AP cells and that this effect varies as a function of age and sex. SP has no significant effect on LH release from AP cells of male and female prepubertal rats. After day 30 a sharp increase in the response to SP occurs in both sexes. This level of responsiveness continues through adulthood in AP cells from the female rat. In contrast, AP cells from male rats failed to respond during adulthood (over 50 days of age) but were highly responsive during the peripubertal period (30-35 days). The possibility that the responsiveness to SP is influenced by the endocrine status of the animal was investigated by exposing AP cells from responding animals to androgens in vivo and in vitro. It was found that AP cells from female rats treated with androgen were less responsive to 100nM SP but did respond at higher doses of SP. SP effects on AP function were further analyzed in experiments using radioligand binding assays to assess possible changes in SP receptor number or affinity as related to age and sex. In AP membranes from female rats, maximum binding is 8-fold higher (Bmax=4.2 pmo1/mg membrane protein) than in AP membranes from male rats (Bmax=560fmo1/ mg membrane protein). These studies suggest a role for SP as a secondary regulator of LH secretion with possible physiological significance for reproductive function.
    DOI
    10.13028/tyhs-8082
    Permanent Link to this Item
    http://hdl.handle.net/20.500.14038/31424
    Rights
    Copyright is held by the author, with all rights reserved.
    ae974a485f413a2113503eed53cd6c53
    10.13028/tyhs-8082
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      CIS/SOCS Proteins in Growth Hormone Action: A Dissertation

      Du, Ling (2000-10-01)
      CIS/SOCS (cytokine-inducible SH2 protein/suppressor of cytokine signaling) are a family of proteins that are thought to act as negative regulators of signaling by erythropoetin, interleukin-6 and other cytokines whose receptors are related to the growth hormone receptor (GHR), and like growth hormone (GH), signal through the JAK/STAT pathway. We examined the possibility that CIS/SOCS proteins may also be involved in GH signaling, in particular, in termination of the transient insulin-like effects of GH. mRNAs for CIS, SOCS3, and to a lesser extent SOCS1 were detectable by Northern blot analysis of rat adipocyte total RNA, and the expression of CIS and SOCS3 was markedly increased 30 min after incubation with 500 ng/ml hGH. Both CIS and SOCS3 were detected in adipocyte extracts by immunoprecipitation and immunoblotting with their corresponding antisera. GH stimulated the tyrosine phosphorylation of a 120 kDa protein (p120) that was co-precipitated from adipocyte extracts along with αCIS and detected in Western blots with phospho-tyrosine antibodies. However, no tyrosine phosphorylated proteins in these cell extracts were immunoprecipitated with antibodies to CIS3/SOCS3. p120 was later identified as the GHR based on the observations that two GHR antibodies recognized p120 in scale-up experiments and that p120 and the GHR share several characteristics, including their molecular weights, tyrosine phosphorylation upon GH stimulation, interaction with CIS, similar extent of glycosylation as judged by electrophoretic mobility shift after Endo F digestion, comparable mobility shifts upon thrombin digestion, and N-terminal histidine-tagging. The findings, however, do not rule out the possibility that there might be other tyrosine phosphorylated 120 kDa protein(s) that interact with CIS and contribute to the p120 signal, as well as the GHR. Further studies of the association of CIS with the GHR revealed that CIS might selectively interact with multiply tyrosine phosphorylated forms of the GHR, and these tyrosines are likely located near the carboxyl end of the GHR. Overexpression of CIS partially inhibited GH-induced STAT5 phosphorylation in CHO cells. Studies in freshly isolated and GH-deprived (sensitive) adipocytes revealed that the abundance of CIS does not correlate with the termination of the insulin-like effects of GH or the emergence of refractoriness. Neither the association of CIS with the GHR nor the tyrosine phosphorylation status of the GHR, JAK2 and STAT5 appear responsible for refractoriness in adipocytes. These data imply that some negative regulators other than CIS might contribute to the termination of GH-induced insulin-like effects in adipocytes.
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      Maternal 3,3'-Diiodothyronine Sulfate Formation from Guinea Pig Placenta Perfused with 3,3',5-Triodothyronine

      Wu, Sing-Yung; Emerson, Charles H.; Tjioe, Edward; Chen, Dong-Bao (2021-09-01)
      OBJECTIVE: Serum 3, 3',5-triiodothyronine (T3) remains low in near-term fetus to prevent the growing fetus from undue exposure to its active catabolic effect in mammals. The present study was undertaken to gain insight in the role of placenta in T3 metabolism, fetal to maternal transfer of T3, and its metabolites by in situ placenta perfusion with outer-ring labeled [(125)I]-T3 in pregnant guinea pig, a species showing increased sulfated 3, 3'-diiodothyronine (T2S) levels in maternal serum in late pregnancy (term = 65 days), similarly to humans in pregnancy. MATERIALS AND METHODS: One-pass placenta perfusions performed on pregnant guinea pigs were studied between 58 - 65 days of gestation. In two separate experiments, the umbilical artery of the guinea pig placenta was perfused in situ at 37 degrees C with outer-ring labeled [(125)I]-T3. Maternal sera and umbilical effluents were obtained for analysis at the end of a 60-minute perfusion, when the steady-state levels of radioactivity were reached in the placenta effluent after 30-minute. RESULTS: Sulfated [(125)I]-T2S was readily detected in the maternal serum as the major metabolite of T3 following the perfusion of placenta with [(125)I]-T3, suggesting that placental inner-ring deiodinase and sulfotransferase may play an important role in fetal T3 homeostasis and in the fetal to maternal transfer of sulfated iodothyronine metabolites. CONCLUSIONS: The expression of type 3 deiodinase (D3) and thyroid hormone sulfotransferase activity in placenta may play an important role to protect developing organs against undue exposure to active thyroid hormone in late gestation in the fetus. The combined activities of D3 and sulfotransferase promoted a placental transfer of T2S into maternal circulation. The maternal circulation of T2S is fetal T3 in origin and its role as a fetal thyroid function biomarker deserves further evaluations and studies.
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      Expression of mitochondrial membrane-linked SAB determines severity of sex-dependent acute liver injury

      Win, Sanda; Min, Robert W. M.; Chen, Christopher Q.; Zhang, Jun; Chen, Yibu; Li, Meng; Suzuki, Ayako; Abdelmalek, Manal F.; Wang, Ying; Aghajan, Mariam; et al. (2019-09-05)
      SAB is an outer membrane docking protein for JNK mediated impaired mitochondrial function. Deletion of Sab in hepatocytes inhibits sustained JNK activation and cell death. Current work demonstrated that increasing SAB enhanced the severity of APAP liver injury. Female mice were resistant to liver injury and exhibited markedly decreased hepatic SAB protein expression versus males. The mechanism of SAB repression involved a pathway from ERalpha to p53 expression which induced miR34a-5p. miR34a-5p targeted the Sab mRNA coding region, repressing SAB expression. Fulvestrant or p53 knockdown decreased miR34a-5p and increased SAB in females leading to increased injury from APAP and TNF/galactosamine. In contrast, ERalpha agonist increased p53 and miR34a-5p which decreased SAB expression and hepatotoxicity in males. Hepatocyte-specific deletion of miR34a also increased severity of liver injury in females, which was prevented by GalNAc-ASO knockdown of Sab. Similar to mice, premenopausal human females also expressed high hepatic p53 and low SAB levels while age-matched males expressed low p53 and high SAB levels, but there was no sex difference of SAB expression in postmenopause. In conclusion, the level of SAB expression determined the severity of JNK dependent liver injury. Females expressed low hepatic SAB protein levels due to an ERalpha-p53-miR34a pathway which repressed SAB expression, accounting for resistance to liver injury.
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