Navegando por Assunto "Prolactina"

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Acesso aberto (Open Access)
Avaliação do efeito protetor da prolactina em linfócitos expostos a ação do metilmercúrio
(Universidade Federal do Pará, 2012-05-23) JESUS, Maria Izabel de; DINIZ, Domingos Luiz Wanderley Picanço; http://lattes.cnpq.br/9601463988942971
Mercury can be found in several forms, as being organic methylmercury (MeHg), considered the most toxic. Readily absorbed orally, accumulates in the food chain and is amplified in aquatic carnivores, especially in fish, hence the greater risk to populations that preferentially feed on them, such as riparian Amazonian populations. The neurotoxic effect of this form of mercury has been widely demonstrated by epidemiological and experimental studies. Some of these studies have also shown that hormones and antioxidants may act by protecting the body against the deleterious effects of mercury. Prolactin is a hormone that has such protective action, but also acts as a proinflammatory cytokine. Since MeHg can also act as an immunotoxic substance, we have studied the cytoprotective action of PRL in continuous cultures of strain B95-A primate lymphocytes in order to assess their vulnerability to MeHg and its responsiveness to the action of PRL. In order to assess the functional integrity of lymphocytes exposed to MeHg we used to test color reaction for 3 - (4,5-dimethylthiazol-2-yl) -2,5-diphenyl tetrazolium bromide (MTT), which detects activity mitochondrial metabolism. To evaluate the immune response of lymphocytes, measures of tumor necrosis factor alpha (TNF α) concentration in the middle were performed by ELISA. It is a proinflammatory cytokine released in response to cellular injury from different causes, including oxidative stress, one of the most obvious acute effects of MeHg, and this cytokine also be able to answer prolactin regulation in human lymphocytes. After 18 hours of cultivation exposure to increasing concentrations of the metal (0.1, 1, 5, 10 and 50 mM) showed significant decrease in dose-dependent cell viability from 1 mM (35%) and progressively up to 50 mM (80%), when few intact cells were found in the cultivation. A biphasic effect in a "bell" shaped occurred in the release of TNF-α, where lower concentrations of MeHg inhibited (0.1 and 1 mM) stimulated the intermediate (5 mM) and the two largest (10 and 50 mM) returned to inhibit. Prolactin also decreased the cell viability by about 30% only at the highest dose (10 nM).Moreover, at a dose of 1 nM prevented PRL 40% decrease in cell viability due to exposure to 5 mM MeHg. This dose of 1 nM PRL was the only one to stimulate the release of TNF-α, but curiously reversed the release of this cytokine when combined with 5 mM of MeHg, concentrations that also stimulated the secretion of TNF-α. The results confirmed the toxicity of MeHg to lymphocytes of primates (strain B95-A) and its reversion by possible protective action of PRL. A biphasic effect on the secretion of TNF α resulted from MeHg exposure, suggesting the presence of different mechanisms of cytotoxic action resulting from mercury. Moreover, PRL was less effective in stimulating the secretion of that cytokine, reversing this response when the associated with MeHg. However, these results are preliminary and require a more accurater study for their complete elucidation.
Acesso aberto (Open Access)
Avaliação in vivo do potencial efeito protetor da prolactina contra danos causados pelo metilmercúrio
(Universidade Federal do Pará, 2022-04) CUNHA, Lorena Araújo da; ROCHA, Carlos Alberto Machado da; http://lattes.cnpq.br/5789536737681588; BURBANO, Rommel Mario Rodriguéz; http://lattes.cnpq.br/4362051219348099; https://orcid.org/0000-0002-4872-234X
Biodegradable metals, such as mercury, accumulate in living organisms throughout their lives (bioaccumulation) and also in food webs (biomagnification), and can reach high concentrations in humans. Human contamination by mercury found in drinking water and food can be common, especially in riverine communities that depend on fish as their main source of protein. In vitro studies with human cell lines exposed to methylmercury showed that prolactin has cytoprotective properties against cytotoxic and mutagenic effects of this metal, and can act as a co-mitogenic factor and apoptosis inhibitor. The present study investigated, in vivo, the protective potential of prolactin against the toxic effects of methylmercury in mammals, using the mouse (Mus musculus) as a model. Biomarkers of genotoxicity (comet assay and micronucleus test) and oxidative stress (lipid peroxidation and activity of CAT and SOD enzymes), together with histological (in liver, kidney and brain tissue samples) and biochemical (renal and hepatic and measurement of Hg and PRL in the blood), were used to verify the protective potential of prolactin in mice exposed to methylmercury. It was observed, in a more expressive way, a reduction in the alterations of the renal and hepatic biochemical parameters and of the mutagenic effects in the presence of prolactin, in comparison with the isolated effects of the metal. When prolactin was used together with the metal, a decrease in histological damage and an increase in SOD enzyme activity were also observed. The study results indicate that prolactin has protective effects against toxic impacts of methylmercury.
Acesso aberto (Open Access)
Efeitos protetores da prolactina em cultivo glial de córtex de ratos expostos ao metilmercúrio
(Universidade Federal do Pará, 2008-04-04) SANTOS, Andréa Cristina Monteiro dos; DINIZ, Domingos Luiz Wanderley Picanço; http://lattes.cnpq.br/9601463988942971
Methylmercury (MeHg) is a compound highly neurotoxic and its degenerative mechanisms are not very clear yet. In Central Nervous System, MeHg is mostly uptake by astrocytes, decreasing neuronal exposition. Studies demonstrated that prolactin (PRL) has mitogenic effects on astrocytes and it can regulate pro-inflammatories cytokines expression. The aim of this work was to verify the protective effects of PRL on disturbs provoked by MeHg on cellular viability, morphology, GFAP (glial fibrillary acidic protein) expression, mitogenesis and release of interleukin-1β in glia primary culture of cerebral cortex of newborn rats, with astrocytes in focus. Glia primary culture were exposed to differents concentrations of MeHg (0,1, 1, 5 e 10 μM) in differents time intervals (2, 4, 6, 18 e 24 h) in medium with fetal bovine serum 10%. Results demonstrated progressive decreasing of 20% e 62% on cellular viability after exposed to 5 e 10 μM MeHg for 24 h, respectively, by MTT [3- (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay and disturbs in the GFAP expression and distribution. Differents concentrations of PRL (0.1, 1 e 10 nM) were added in free serum medium to evaluate it proliferative action. This was confirmed by mitogenesis induction around 4.5x in 18h at 10 mM PRL. In this conditions (free serum) were evaluated the effects of co-treatment of 1 nM PRL + 5 μM MeHg on cellular viability, morphology, GFAP expression, mitotic index and release of IL-1β. PRL attenuated disturbs caused by MeHg, increasing viability in 33%, GFAP expression, cellular proliferation (4x), and attenuating morphologic alterations like nuclear picnosis and lisis. These findings prove that PRL can act like a cytoprotective agent in primary culture of glia, particularly in astrocytes, in addition to its mitogenic effects.
Acesso aberto (Open Access)
Methylmercury inhibits prolactin release in a cell line of pituitary origin
(Universidade Federal do Pará, 2015-08) MAUÉS, Luis Antônio Loureiro; MACCHI, Barbarella de Matos; CRESPO LÓPEZ, Maria Elena; NASCIUTTI, Luís Eurico; DINIZ, Domingos Luiz Wanderley Picanço
Heavy metals, such as methylmercury, are key environmental pollutants that easily reach human beings by bioaccumulation through the food chain. Several reports have demonstrated that endocrine organs, and especially the pituitary gland, are potential targets for mercury accumulation; however, the effects on the regulation of hormonal release are unclear. It has been suggested that serum prolactin could represent a biomarker of heavy metal exposure. The aim of this study was to evaluate the effect of methylmercury on prolactin release and the role of the nitrergic system using prolactin secretory cells (the mammosomatotroph cell line, GH3B6). Exposure to methylmercury (0-100 μM) was cytotoxic in a time- and concentration-dependent manner, with an LC50 higher than described for cells of neuronal origin, suggesting GH3B6 cells have a relative resistance. Methylmercury (at exposures as low as 1 μM for 2 h) also decreased prolactin release. Interestingly, inhibition of nitric oxide synthase by N-nitro-L-arginine completely prevented the decrease in prolactin release without acute neurotoxic effects of methylmercury. These data indicate that the decrease in prolactin production occurs via activation of the nitrergic system and is an early effect of methylmercury in cells of pituitary origin.
Acesso aberto (Open Access)
Níveis de mercúrio, prolactina e interleucina 10 em mulheres em idade reprodutiva e puérperas dos municípios de Itaituba e Ananindeua, Pará
(Universidade Federal do Pará, 2012-05-02) JESUS, Iracina Maura de; DINIZ, Domingos Luiz Wanderley Picanço; http://lattes.cnpq.br/9601463988942971
The ability of interfering in the immunological and endocrine organic systems has been attributed to the mercury (Hg), besides the nervous and renal systems frequently affected by this toxicant agent. Women in fertile age or pregnant constitute a vulnerable group for those effects, in relation to themselves and their fetus. The mercury exposure was assessed as well as the prolactin (PRL) and interleukin-10 (IL-10) levels in 144 women (in the post-partum and about one year later) of Itaituba, area under environmental Hg impact and in women of the metropolitan area of Belém, most of all from Ananindeua, area without known Hg impact (156 puerperal women and 156 non-puerperal). Total Hg (Hg-t) analyses in whole blood were carried out by Atomic Absorption Spectrometry Cold Vapor. Serum analyses of PRL were made by Enzyme Immunoassay with final detection by fluorescence and IL-10 serum analyses were accomplished by Enzyme Immunoassay of Solid Phase. Demographic and epidemiological data were obtained through semi-structured questionnaire. Puerperal women of Itaituba presented average of Hg-t, PRL and IL-10 of 13.93 μg/l, 276.20 ng/ml and 39.54 pg/ml, respectively. Puerperal women of Ananindeua presented respective Hg-t, PRL and IL-10 averages of 3.76 μg/l, 337.70 ng/ml and 4.90 pg/ml. Non-puerperal women of Itaituba presented Hg-t mean of 12.68 μg/l, PRL mean of 30.75 ng/ml and IL-10 mean of 14.20 pg/ml. Mean of Hg-t, PRL and IL-10 in non-puerperal women from Ananindeua were of 2.73 μg/l, 17.07 ng/ml and 1.49 pg/ml, respectively. Levels of Hg-t, PRL and IL-10 were higher in Itaituba (p<0.0001), except in PRL levels of puerperal women, higher in Ananindeua. Similar Hg levels in women of Itaituba in two assessment (p=0.7056) and positive correlation suggest continuity of exposure (r=0.4736, p<0.0001). The main predictor variable of mercury levels was the fish consumption in the linear and logistic multiple regression models. Parity and IL-10 levels were positively associated with PRL in puerperal women of Itaituba while newborn weight and IL-10 levels presented positive association with PRL in puerperal women of Ananindeua. IL-10 was negatively associated with PRL in non-puerperal women from Itaituba (p=0.0270) and positive association in Ananindeua (p=0.0266). Levels of Hg-t showed negative association with PRL in puerperal women and positive association with working in garimpo (p=0.0173) (the last one was also important for non-puerperal women) in Itaituba, according logistic models. IL-10 was positively associated with recent morbidity in puerperal women of Itaituba (p=0.0210), negatively with ingestion of alcoholic beverages (p=0.0178) and positively with working in garimpo in non-puerperal women (p=0.0199). The chronic Hg exposure of women from Itaituba, difference among the Hg, PRL and IL-10 levels in exposed women compared with non exposed group and association with relevant epidemiological variables, suggest the possibility of Hg impacts in the women's immunoendocrine system in Itaituba, calling attention for the health surveillance of this population and the possible use of assessment biomarkers as PRL.
Acesso aberto (Open Access)
Stimulatory effects of adenosine on prolactin secretion in the pituitary gland of the rat
(2002-07) DINIZ, Domingos Luiz Wanderley Picanço; VALENÇA, Marcelo Moraes; FAVARETTO, Ana Lucia Vianna; RODRIGUES, José Antunes
We investigated the effects of adenosine on prolactin (PRL) secretion from rat anterior pituitaries incubated in vitro. The administration of 5-N- methylcarboxamidoadenosine (MECA), an analog agonist that preferentially activates A2 receptors, induced a dose-dependent (1 nM to 1 µM) increase in the levels of PRL released, an effect abolished by 1,3-dipropyl-7-methylxanthine, an antagonist of A2 adenosine receptors. In addition, the basal levels of PRL secretion were decreased by the blockade of cyclooxygenase or lipoxygenase pathways, with indomethacin and nordihydroguaiaretic acid (NDGA), respectively. The stimulatory effects of MECA on PRL secretion persisted even after the addition of indomethacin, but not of NDGA, to the medium. MECA was unable to stimulate PRL secretion in the presence of dopamine, the strongest inhibitor of PRL release that works by inducing a decrease in adenylyl cyclase activity. Furthermore, the addition of adenosine (10 nM) mimicked the effects of MECA on PRL secretion, an effect that persisted regardless of the presence of LiCl (5 mM). The basal secretion of PRL was significatively reduced by LiCl, and restored by the concomitant addition of both LiCl and myo-inositol. These results indicate that PRL secretion is under a multifactorial regulatory mechanism, with the participation of different enzymes, including adenylyl cyclase, inositol-1-phosphatase, cyclooxygenase, and lipoxygenase. However, the increase in PRL secretion observed in the lactotroph in response to A2 adenosine receptor activation probably was mediated by mechanisms involving regulation of adenylyl cyclase, independent of membrane phosphoinositide synthesis or cyclooxygenase activity and partially dependent on lipoxygenase arachidonic acid-derived substances.