Estudo estereológico em rins de ratos pré-púberes e adultos submetidos a estresse crônico

Abstract

Stress is the body's response to harmful stimuli. In situations, the hypothalamic-pituitary-adrenal axis activated is increasing the secretion of cortisol and catecholamines. Therewith, a homeostasis of the organism affected can be by physiopathological changes, being able to generate imbalance of the organism in front of the stress stimulus. The functional unit can then be affected by endocrine mechanisms linked to stress, which may compromise renal function. Evaluate, by stereological methods, the kidneys of rats submitted to chronic stress before (prepubertal) and after puberty (adults), both immediately after stress stimuli and late. Seventy-six male Wistar rats were used in the experiments. Four groups were submitted to chronic stress and four control groups, subdivided into immediate groups (euthanasia 24 hours after the stress phase) and late (euthanasia 6 weeks after the end of the stress phase). Experiments were performed in two different age groups: four weeks of age (prepubertal rats) and ten weeks of age (adult rats). For each of these groups of animals submitted to stress, control groups of the same age were also analyzed. Animals submitted to chronic stress were restricted to movement daily in the morning, for six weeks during two hours. The animals of control groups were kept in cages, without food and water during two hours daily, also in the morning. After euthanasia, the kidney was fixed in 3.7% buffered formalin, processed and included in paraffin. The renal weight and volume, glomerular volumetric density (Vv [Glom]), mean glomerular volume (VWGV) and number of glomeruli per kidney were evaluated. Data were compared by unpaired Student t test, considering p<0.05 as significant. The study was approved by the ethics committee of the State University of Rio de Janeiro, under protocol number CEUA / 007/2018. Renal weight and volume had a decrease of 10.8 and 9%, respectively, in the immediate pre-pubertal chronic stress group in relation to their control. The cortex / non-cortex ratio of the EI4 group demonstrated a 4.4% increase in the cortical region when the control group CI4. The immediate and late prepubertal groups presented a reduction in Vv [Glom] in 17.4 (p= 0,0119) and 14.1% (p=0,0174), respectively, in relation to their controls. On the other hand, the stressed animals of the immediate and late adult groups had a decrease in Vv [Glom] in 15.8 (p= 0,0142) and 13.6%, respectively, in comparison to their control groups. Regarding the VWGV evaluation, no significant difference was found. Regarding the number of glomeruli per kidney, the immediate pre-pubertal group presented a glomerular loss in comparison to its control of 20.9%. A similar result was observed when comparing the pre-pubertal group with its control, presenting a reduction of 19.8%. The adult animals evaluated immediately and late had a reduction in the number of glomeruli per kidney of 33.1% and 16.6% respectively, in relation to their controls. Chronic stress leads to a reduction in the number of glomeruli and there is no progression of the loss with the interruption of the stressor stimulus.