Efeitos do estresse crônico sobre o timo e o hipocampo de ratos jovens e senis submetidos a desafio imunológico e tratamento com hormônio do crescimento (modelo experimental)

• Autor(a) principal: Ferreira, Anna Paula Baptista Ribeiro
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1446
• topic: Estresse; Senilidade; Ratos; Stress; Senility; Rats; CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA::PATOLOGIA ANIMAL

To evaluate the effect of moderate chronic stress on aging, it had been developed an experimental model using young and old rats. The rats, males and females, in a total of 80 animals, were divided into four treatments being them control (C), stress (E), stress associated with an immune challenge (E+D) and E+D with use of growth hormone (E+D+GH). The experiment lasted 28 days, with applicationof different stressors on alternate days. At the end of day 28, the animals were sacrificed and material was collected for analysis. The thymus, analyzed histologically and morphometrically showed changes consistent with the aging process, showing a lack of demarcation of cortical and medullary layers, decreasing the percentage of medullary in relation to cortical, both for older as for younger animals subjected to stress protocols. The use of GH promoted a thymus hypertrophy in older rats. However, the sex did not influence the thymus layers (p > 0.005). Testosterone was not influenced by the protocols, but was significantly altered for sex and sex protocol X interaction (p < 0.005), unlike estrogen levels that were influenced by the sex and the protocol (p < 0.001) with increase in animals of protocols E+D and E+D+GH, suggesting an immune response to stress. The weight of the brain suffered influence of sex and protocols, with a significance level of 0.005. The granular cell layer of the dentate gyrus (GD) and CA4 region of the hippocampus were also analyzed to verify the histological and morphometric changes. Histologically, the old rats of protocol E+D+GH, of both sexes showed less dispersion of the granular layer and decreased number of hipercor neurons, suggesting a neuro-protective effect for GH. The immune histochemical expression of immune proteasomes LMP2, LMP7, and &#945;7 PA28&#945; were assessed in the hippocampus. PA28&#945; and &#945;7 showed strongly positive immune staining in all animals. The expression of anti-LMP2 and anti-LMP7 was observed in old and young rats subjected to stress; suggesting stress simulates the process of brain aging. The use of GH decreased the expression of LMP2 in old rats and has a negative immunoreaction for LMP7. That s resulted suggesting with the stress is related to the morphologic changes consistent with the aging process in thymus and hippocampus of the young rats and changed the hormonal estradiol levels in males and females, young and old rats. The use of GH promoted changed in thymus and hippocampus of the old rats.