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- Author: F M Sánchez x
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Medizinische Klinik Innenstadt, Institute of Molecular Animal Breeding and Biotechnology, Division of Endocrinology, Institute for Molecular Medicine and Cell Research, Laboratory of Mouse Genetics, Ludwig-Maximilians University, Ziemssenstr. 1, 80336 Munich, Germany
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Medizinische Klinik Innenstadt, Institute of Molecular Animal Breeding and Biotechnology, Division of Endocrinology, Institute for Molecular Medicine and Cell Research, Laboratory of Mouse Genetics, Ludwig-Maximilians University, Ziemssenstr. 1, 80336 Munich, Germany
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Data on the involvement of aldosterone in the regulation of the renin–angiotensin–aldosterone system (RAAS) in rodents are still scarce, partly due to the high sample volumes needed by commercially available assays and to the very low aldosterone concentrations present. We have developed a highly sensitive and non-isotopic immunoassay, requiring a volume of only 50 μl serum for a duplicate measurement, employing a highly specific monoclonal antibody against aldosterone. The assay was validated in human and mouse samples and exhibited a linear working range from 10 to 1000 pg/ml. Values obtained after a chromatographic purification step correlated significantly to the dichloromethane extraction ordinarily used. Basal aldosterone values were measured in 75 mouse hybrids and found within the linear range (173±21 pg/ml), with no significant difference between males and females. Additionally, we show an increase in serum aldosterone in mice from 3 to 11 weeks of age. Mice of the same genetic background were treated with dexamethasone intraperitoneally (n=7), resulting in significantly decreased concentrations (35±3 vs 114±33 pg/ml in controls; P<0.001). In contrast, adrenocorticotropic hormone resulted in significantly increased serum aldosterone (603±119 pg/ml; n=7; P<0.001), as did the physiological stimulation of the RAAS by a high K+/low Na+ diet (1369±703 vs 172±36 pg/ml). In conclusion, we have developed and validated an extremely sensitive assay for determination of aldosterone concentrations from very small serum samples, which could be especially useful in pharmacological intervention studies in rodent models.
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Telomerase is a ribonucleoprotein DNA polymerase that has been associated with cell proliferation, cell survival and apoptosis inhibition. Telomerase is regulated by specific growth factors, cytokines and hormones. The present study examines the effect of GH on telomerase activity and identifies the signal transduction pathway involved in this process in Chinese hamster ovary (CHO)4 cells, which express rat GH receptor cDNA. Telomeric repeat amplification protocol assays demonstrated that treating CHO4 cells with increasingly high doses of GH up-regulated telomerase activity with the maximum activation at 24 h. Similarly, GH activated telomerase in another cell system, primary cultures of rat hepatocytes. The telomerase activation in CHO4 cells was produced with an increase in hamster telomerase catalytic subunit (hamTERT) mRNA expression. The telomerase activity induced by GH was specifically blocked by the phosphatidylinositol 3′-kinase (PI3-K) inhibitor, LY294002, but not by the MAP kinase kinase inhibitor, PD98059. These findings suggest that GH could activate telomerase through the direct activation of TERT transcription, as well as through the PI3-K signalling pathway.
IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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IBYME–CONICET Buenos Aires, C1428ADN, Argentina. Departamento de Química Biológica, Facultad de Ciencas Exactas y Naturales, Buenos Aires C1428EGA, Argentina
Departmento de Fistologia, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155 5°, Buenos Aires C1121ABG, Argentina
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The present study was designed to investigate the effect of lipopolysaccharide (LPS) on the expression levels and activities of the nitric oxide synthase (NOS) and heme oxygenase (HO) systems in the rat adrenal gland. Both enzymatic activities were significantly increased in this tissue after in vivo treatment with LPS. The concurrent induction of the HO-1, NOS-1, and NOS-2 gene products was also detected as both mRNAs and protein levels were augmented by this treatment in a time-dependent way. A significant interaction between both signaling systems was also demonstrated as in vivo blockage of NOS activity with N(G)-nitro-L-arginine methyl ester (L-NAME) resulted in a significant reduction in HO expression and activity levels, while an increase in NOS activity was observed when HO was inhibited by Sn-protoporphyrin IX (Sn-PPIX). As both NOS and HO activities have been previously involved in the modulation of adrenal steroidogenesis, we investigated the participation of these signaling systems in the adrenal response to LPS. Our results showed that acute stimulation of steroid production by ACTH was significantly increased when either NOS or HO activities were inhibited. We conclude that adrenal NOS and HO can be induced by a non-lethal dose of endotoxin supporting a modulatory role for these activities in the adrenal response to immune challenges.
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Several investigators have suggested that certain hydroxylated metabolites of 17β-estradiol (E2) are the proximate carcinogens that induce mammary carcinomas in estrogen-sensitive rodent models. The studies reported here were designed to examine the carcinogenic potential of different levels of E2 and the effects of genotoxic metabolites of E2 in an in vivo model sensitive to E2-induced mammary cancer. The potential induction of mammary tumors was determined in female ACI rats subcutaneously implanted with cholesterol pellets containing E2 (1, 2, or 3 mg), or 2-hydroxyestradiol (2-OH E2), 4-hydroxyestradiol (4-OH E2), 16α-hydroxyestradiol (16α-OH E2), or 4-hydoxyestrone (4-OH E1) (equimolar to 2 mg E2). Treatment with 1, 2, or 3 mg E2 resulted in the first appearance of a mammary tumor between 12 and 17 weeks, and a 50% incidence of mammary tumors was observed at 36, 19, and 18 weeks respectively. The final cumulative mammary tumor incidence in rats treated with 1, 2, or 3 mg E2 for 36 weeks was 50%, 73%, and 100% respectively. Treatment of rats with pellets containing 2-OH E2, 4-OH E2, 16α-OH E2, or 4-OH E1 did not induce any detectable mammary tumors. The serum levels of E2 in rats treated with a 1 or 3 mg E2 pellet for 12 weeks was increased 2- to 6-fold above control values (~30 pg/ml). Treatment of rats with E2 enhanced the hepatic microsomal metabolism of E2 to E1, but did not influence the 2- or 4-hydroxylation of E2. In summary, we observed a dose-dependent induction of mammary tumors in female ACI rats treated continuously with E2; however, under these conditions 2-OH E2, 4-OH E2, 16α-OH E2, and 4-OH E1 were inactive in inducing mammary tumors.
