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      Polimorfismos del receptor D2 Translated title: D2 receptor polymorphisms

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          Abstract

          Los prolactinomas son tumores bien diferenciados que se originan en las células lactotropas pituitarias, una línea celular que secreta fisiológicamente prolactina (PRL). A nivel hipofisario, la dopamina está implicada en la regulación de la secreción de PRL por las células lactotropas y este efecto inhibitorio está mediado por la activación del receptor de prolactina tipo 2 (DRD2). Hay varios polimorfismos del DRD2, el primero y más estudiado es TaqI A1; está demostrado que este alelo se encuentra asociado a una reducción de la actividad cerebral dopaminérgica, además de observarse una reducción en su capacidad de unión de aproximadamente un 30%. Este alelo se ha vinculado con una menor densidad de DRD2 en el cuerpo estriado, especialmente en el putamen y caudado ventral, y la cantidad de DRD2 en portadores del alelo A1 fue un 30-40% más bajo que en los no portadores (es decir, TaqI A2 homocigotos). En la literatura, hay evidencia que apoya la posible participación de los polimorfismos DRD2 en la regulación de la secreción hormonal.

          Translated abstract

          Prolactinomas are well differentiated tumours that originate in the pituitary lactotrope cells, a cell line that physiologically secretes prolactin (PRL). At pituitary level, dopamine is involved in the regulation of PRL secretion by lactotropes, and this inhibitory effect is mediated by activation of prolactin type 2 receptor (DRD2). Of the several DRD2 polymorphisms, the first and most studied is TaqI A1. It has been demonstrated that this allele is associated with a reduced dopaminergic brain activity, and a reduction in its binding capacity of approximately 30% also being observed. This allele was associated with a lower density of DRD2 in the striatum, especially in the putamen and ventral caudate. The amount of DRD2 in A1 allele carriers was 30 - 40% lower than in non-carriers (this is, TaqI A2 Homozygotes). There is evidence in the literature, that supports the possible involvement of DRD2 polymorphisms in the regulation of hormonal secretion.

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          Most cited references 45

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          The prevalence of pituitary adenomas: a systematic review.

          Pituitary adenomas display an array of hormonal and proliferative activity. Once primarily classified according to size (microadenomas, or = 1 cm), these tumors are now further classified according to immunohistochemistry and functional status. With these additional classifications in mind, the goals of the current study were to determine the prevalence of pituitary adenomas and to explore the clinical relevance of the findings. The authors conducted a metaanalysis of all existing English-language articles in MEDLINE. They used the search string (pituitary adenoma or pituitary tumor) and prevalence and selected relevant autopsy and imaging evaluation studies for inclusion. The authors found an overall estimated prevalence of pituitary adenomas of 16.7% (14.4% in autopsy studies and 22.5% in radiologic studies). Given the high frequency of pituitary adenomas and their potential for causing clinical pathologies, the findings of the current study suggest that early diagnosis and treatment of pituitary adenomas should have far-reaching benefits.
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            Synonymous mutations in the human dopamine receptor D2 (DRD2) affect mRNA stability and synthesis of the receptor.

             J. Duan (2003)
            Although changes in nucleotide sequence affecting the composition and the structure of proteins are well known, functional changes resulting from nucleotide substitutions cannot always be inferred from simple analysis of DNA sequence. Because a strong synonymous codon usage bias in the human DRD2 gene, suggesting selection on synonymous positions, was revealed by the relative independence of the G+C content of the third codon positions from the isochoric G+C frequencies, we chose to investigate functional effects of the six known naturally occurring synonymous changes (C132T, G423A, T765C, C939T, C957T, and G1101A) in the human DRD2. We report here that some synonymous mutations in the human DRD2 have functional effects and suggest a novel genetic mechanism. 957T, rather than being 'silent', altered the predicted mRNA folding, led to a decrease in mRNA stability and translation, and dramatically changed dopamine-induced up-regulation of DRD2 expression. 1101A did not show an effect by itself but annulled the above effects of 957T in the compound clone 957T/1101A, demonstrating that combinations of synonymous mutations can have functional consequences drastically different from those of each isolated mutation. C957T was found to be in linkage disequilibrium in a European-American population with the -141C Ins/Del and TaqI 'A' variants, which have been reported to be associated with schizophrenia and alcoholism, respectively. These results call into question some assumptions made about synonymous variation in molecular population genetics and gene-mapping studies of diseases with complex inheritance, and indicate that synonymous variation can have effects of potential pathophysiological and pharmacogenetic importance.
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              Prevalence of pituitary adenomas: a community-based, cross-sectional study in Banbury (Oxfordshire, UK).

              Pituitary adenomas (PAs) are associated with increased morbidity and mortality. The optimal delivery of services and the provision of care for patients with PAs require distribution of the resources proportionate to the impact of these conditions on the community. Currently, the resource allocation for PAs in the health care system is lacking a reliable and an up-to-date epidemiological background that would reflect the recent advances in the diagnostic technologies, leading to the earlier recognition of these tumours. To determine the prevalence, the diagnostic delay and the characteristics of patients with PA in a well-defined geographical area of the UK (Banbury, Oxfordshire). Sixteen general practitioner (GP) surgeries covering the area of Banbury and a total population of 89 334 inhabitants were asked to participate in the study (data confirmed on 31 July 2006). Fourteen surgeries with a total of 81,449 inhabitants (91% of the study population) agreed to take part. All cases of PAs were found following an exhaustive computer database search of agreed terms by the staff of each Practice and data on age, gender, presenting manifestations and their duration, imaging features at diagnosis, history of multiple endocrine neoplasia type 1 and family history of PA were collected. A total of 63 patients with PA were identified amongst the study population of 81,149, with a prevalence of 77.6 PA cases/100,000 inhabitants (prolactinomas; PRLoma: 44.4, nonfunctioning PAs: 22.2, acromegaly; ACRO: 8.6, corticotroph adenoma: 1.2 and unknown functional status; UFS: 1.2/100,000 inhabitants). The distribution of each PA subtype was for PRLoma 57%, nonfunctioning PAs 28%, ACRO 11%, corticotroph adenoma 2% and UFS 2%. The median age at diagnosis and the duration of symptoms until diagnosis (in years) were for PRLoma 32.0 and 1.5, nonfunctioning PAs 51.5 and 0.8, ACRO 47 and 4.5 and corticotroph adenoma 57 and 7, respectively. PRLoma was the most frequent PA diagnosed up to the age of 60 years (0-20 years: 75% and 20-60 years: 61% of PAs) and nonfunctioning PA after the age of 60 years (60% of PAs). Nonfunctioning PAs dominated in men (57% of all men with PA) and PRLoma in women (76% of all women with PA). Five patients (7.9%) presented with classical pituitary apoplexy, with a prevalence of 6.2 cases/100,000 inhabitants. Based on a well-defined population in Banbury (Oxfordshire, UK), we have shown that PAs have a fourfold increased prevalence than previously thought; our data confirm that PAs have a higher burden on the Health Care System and optimal resource distribution for both clinical care and research activities aiming to improve the outcome of these patients are needed.
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                Author and article information

                Contributors
                Role: ND
                Journal
                raem
                Revista argentina de endocrinología y metabolismo
                Rev. argent. endocrinol. metab.
                Sociedad Argentina de Endocrinología y Metabolismo (Ciudad Autónoma de Buenos Aires, , Argentina )
                1851-3034
                April 2017
                : 54
                : 1
                : 29-36
                Affiliations
                Buenos Aires orgnameHospital J. M. Ramos Mejía orgdiv1División Endocrinología Argentina
                Article
                S1851-30342017000100004
                10.1016/j.raem.2016.12.002

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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