Endocrine
The present article shows for the first time that two cell lines derived respectively from a rat glioma (C6 cell line) and from a human astrocytoma (1321N1 cell line) are able to convert testosterone and progesterone into their corresponding 5α-reduced metabolites dihydrotestosterone and dihydroprogesterone. Moreover, both cell lines are also able to convert these metabolites further into their corresponding...
Hyponatremia has been observed in elderly patients treated with the selective serotonin reuptake inhibitor (SSRI) fluoxetine. The pathogenesis of this effect is not known, but enhanced release of vasopressin (VP) and its renal actions may be a possible mechanism. Excess secretion of VP in combination with large fluid intake is known to induce hyponatremia. We determined if chronic fluoxetine administration...
Expression of GnRH receptors increases prior to the onset of the preovulatory surge of LH in sheep. Two experiments were conducted to investigate the interactions of progesterone (P) and estradiol (E) on amounts of mRNA for GnRH receptors and the number of receptors for GnRH. The first study was designed as a 2 × 2 factorial arrangement of treatments to investigate effects of removal of P and the...
Parathyroid hormone-related protein (PTHrP), an important factor in the pathogenesis of humoral hypercalcemia of malignancy, is produced by many normal tissues, including the epidermis, where it is thought to play a role in the regulation of keratinocyte growth and differentiation. Most in vitro studies of normal keratinocytes use monolayer cell cultures, which have limitations, including the inability...
The present experiments were designed in order to elucidate the participation of the developing hypophysis in determining the changing sensitivity of gonadotrophins to gonadotropin-releasing hormone (GnRH) during ontogeny in the rat. To that end, we chose two well defined developmental ages that differ markedly in sexual and ontogenic characteristics of hypophyseal sensitivity to GnRH, 15 and 30 d...
Steroidogenic acute regulatory (StAR) protein mediates the rapid increase in steroid hormone biosynthesis in response to tropic hormones by facilitating transport of cholesterol into the inner mitochondrial membrane. Although our laboratory has recently reported on the hormonal regulation of StAR mRNA in the rat ovary, the same regulation in the human corpus luteum requires analysis. To this end,...
Phytoestrogens can exhibit agonistic actions on estrogen-dependent gene expression in breast cancer cells. Since several different phytoestrogens may be found within a single dietary plant source, we sought to investigate whether estrogen-dependent gene expression may be further influenced by the collective treatment of breast cancer cells with multiple phytoestrogens. Accordingly, we transfected...
The effect of recombinant bovine tumor necrosis factor-α (TNF-α) on steroidogenesis and numbers of bovine ovarian granulosa and thecal cells has been studied, and specific binding sites for 125I-TNF-α on ovarian cells have been determined. Granulosa cells have been examined from small (surface diameter 1–5 mm) follicles, whereas thecal cells from large (≥ 8 mm) follicles were utilized. Increasing...
Although age-related decline in plasma growth hormone (GH) levels is well documented, the possible role of GH in the control of aging is controversial. Overexpression of GH in transgenic mice is associated with reduced life expectancy and numerous symptoms of premature aging. Ames dwarf mice with hereditary GH, prolactin, and thyrotropin deficiency live much longer than their normal siblings. In contrast...
Here we investigate the roles of human testicular orphan receptors, TR2 and TR4, on the gene regulation of the long-terminal repeat of the human immunodeficiency virus type 1 (HIV-LTR). In gel-retardation assays, a palindromic element at the 5′-end of HIV-LTR, 5′-AGGGGTCAGATATCCACTGACCTTT-3′, showed high affinity to TR2 and TR4 with an equilibrium dissociation constant (K d) of 1.11 ± 0.48 (n = 3)...
The aim of this study was to examine the effects of insulin and phorbol 12-myristate 13-acetate (PMA), an activator of classic and novel PKCs, on the translocation of PKC from cytosol to membrane in H4IIE (H4) rat hepatoma cells. Six PKC isoforms were expressed, including PKC-μ and PKC-λ, identified for the first time in this hepatoma cell line. Insulin induced translocation of PKC-δ from the cytosol...
Glucocorticoid hormones potentiate the toxic effects of neuronal stressors. Alteration of gene expression by glucocorticoids could contribute to neuronal susceptibility by downregulating the synthesis of proteins necessary to adapt to challenge. Using heat shock of hippocampal slices as a model for cellular insult, protein synthesis has been examined in response to acute glucocorticoid administration...
Parathyroid hormone (PTH) elicits many of its physiological effects by activating distinct G-proteincoupled signaling cascades that lead to synthesis of cyclic AMP and hydrolysis of phosphatidylinositol 4,5-bisphosphate. Using the nonhydrolyzable photoreactive GTP analog [α-32P]GTP-γ-azidoanilide (GTP-AA) and peptide antisera raised against G-protein α-subunits, we studied coupling of the PTH receptor...
Human TR2 orphan receptor, isolated from the testis and prostate, is a member of the steroid/thyroid hormone receptor superfamily. With the screening of a human genomic library and the combination of primer walking and PCR sequencing, we found that the entire TR2 orphan receptor gene coding region and 5′-untranslated region feature 13 introns and 14 exons, and that the consensus splice sequences (GT-AG)...
To evaluate the effect of nitric oxide (NO·) in human corpus luteum (CL) function, we investigated the expression and the presence of NO· synthase (NOS) in the human CL and the action of NO· on the in vitro luteal steroid production. The expression of endothelial NOS (eNOS) in early, mid-, and late CL was assessed by reverse transcriptase polymerase chain reaction (RT-PCR) and the immunohistochemical...
Shc is a novel type of tyrosine-phosphorylated protein activated in response to a wide variety of polypeptide ligands. In this study, we used immunoprecipitation and immunoblotting to examine the effect of insulin on Shc tyrosine phosphorylation and Shc/GRB2 association in insulin-sensitive tissues of the intact rat. Following an infusion of insulin, Shc was tyrosine-phosphorylated in the liver, skeletal...
This study aims at the identification and functional characterization of glucagon-like peptide 1 (7–36) amide (GLP-1) receptor in islets from Golden Syrian hamsters. Using a polyclonal antibody against rat GLP-1 receptors, Western blotting of the islet proteins revealed two major bands of 44 and 70 kDa, similar to those found in rat islets, RINm5F cells, and HIT-T15 cells. In Northern blots, transcripts...
TNF-α plays a critical role in the cascade of neuroendocrine events during inflammation and septic shock. It also affects the release of pituitary hormones and acts as a growth factor in immune and nonimmune cells. The aim of the present study was to investigate the release of TNF-α from rat anterior pituitary cells and the effect of the steroid medium on its release. Cultured anterior pituitary cells...
The effects of porcine relaxin on arterial blood pressure, heart rate, and the release of vasopressin and oxytocin were investigated in homozygous diabetes insipidus (di/di) Brattleboro and Long-Evans rats. Acute iv injection of relaxin (5 µg) caused a significant increase in mean arterial, systolic and diastolic blood pressures in Long-Evans rats compared with control injections of saline, but had...
Gonadotropin-releasing hormone (GnRH) receptor expression is regulated by estradiol and GnRH itself. The objective of this experiment was to determine the extent to which low levels of estradiol, similar to those observed during the transition from the luteal to the follicular phase of the estrous cycle, and GnRH interact to regulate expression of GnRH receptors and GnRH receptor mRNA. Ewes were ovariectomized...