Stress biomarkers in rats submitted to swimming and treadmill running exercises.

The objective of the present work was to compare stress biomarkers (serum ACTH and corticosterone hormones) during known intensity swimming and treadmill running exercises performed by rats. Adult Wistar rats (n=41) weighing 320-400 g at the beginning and 420-500 g at the end of the experiment, previously adapted to exercise and with Maximal Lactate Steady State (MLSS) already determined were used. The animals were divided into the following subgroups: (1) sacrificed shortly after session of 25 min of exercise (swimming or treadmill) at the MLSS intensity or (2) sacrificed after exhaustive exercise (swimming or treadmill) at intensity 25% higher than MLSS. For comparison, a control group C was sacrificed at rest. Two-way ANOVA was used to identify differences in the stress parameters (P<0.05). At both exercise intensities serum ACTH concentrations were significantly higher for the swimming group compared to running and control groups, while serum corticosterone concentrations in swimming and running groups were significantly higher than in the control group. The differences were more pronounced at the higher intensity (25% higher than MLSS). The swimming group showed higher concentrations for both hormones in relation to the running group. Only acute swimming exercise induced activity of the hypothalamic-pituitary-adrenal axis responses expected to stress: elevations in the serum ACTH and corticosterone concentrations.

Exercise test and glucose homeostasis in rats treated with alloxan during the neonatal period or fed a high calorie diet.

BACKGROUND: Animal models appear well-suited for studies into the role of exercise in the prevention of non-insulin-dependent diabetes mellitus (NIDDM). The aim of the present study was to analyze glucose homeostasis and blood lactate during an exercise swimming test in rats treated with alloxan during the neonatal period and/or fed a high calorie diet from weaning onwards. METHODS: Rats were injected with alloxan (200 mg/kg, i.p.) or vehicle (citrate buffer) at 6 days of age. After weaning, rats were divided into four groups and fed either a balanced diet or a high-caloric diet as follows: C, control group (vehicle + normal diet); A, alloxan-treated rats fed the normal diet; H, vehicle-treated rats fed the high-caloric diet; and HA, alloxan-treated rats fed the high-caloric diet. RESULTS: Fasting serum glucose levels were higher in groups A and AH compared with the control group. The Homeostatic Model Assessment index varied in the groups as follows: H>A>HA = C. There were no differences in free fatty acids or blood lactate concentrations during the swim test. CONCLUSIONS: Alloxan-treated rats fed a normal or high-caloric diet have the potential to be used in studies analyzing the role physical exercise plays in the prevention of NIDDM.

Biomarcadores de estresse em ratos exercitados por natação em intensidades igual e superior à máxima fase estável de lactato / Biomarkers of stress in rats exercised in swimming at intensities equal and superior to the maximal estable lactate phase

INTRODUÇÃO: O estresse alcançado durante exercício agudo/crônico é relevante, pois altos índices de estresse podem prejudicar o bem-estar dos animais. As concentrações dos hormônios adrenocorticotrófico (ACTH) e corticosterona, bem como as concentrações de ácido ascórbico e colesterol das glândulas adrenais são importantes biomarcadores de estresse. OBJETIVO: Analisar a sensibilidade de diferentes biomarcadores de estresse em ratos durante exercício agudo de natação em diferentes intensidades. MÉTODO: Ratos (18) adaptados à natação foram submetidos a três testes de 25 minutos suportando cargas 5,0; 5,5 e 6,0 por cento do peso corporal (PC), para obtenção da máxima fase estável de lactato (MFEL). Em seguida, os animais foram divididos em dois grupos: M (n = 9), sacrificado após 25 minutos de exercício na intensidade de MFEL e S (n = 9), sacrificado após exercício exaustivo, em intensidade 25 por cento superior a MFEL. Para comparações, um grupo controle C (n = 10) foi sacrificado em repouso. RESULTADOS: As concentrações séricas de ACTH e corticosterona foram superiores após exercício em ambas as intensidades comparadas com o grupo controle (P < 0,05). As concentrações de ACTH e corticosterona do grupo S foram, ainda, maiores do que as do grupo M (P < 0,05). As concentrações de colesterol e ácido ascórbico na adrenal dos grupos exercitados (M e S) foram inferiores às do grupo controle (P < 0,05). Não houve diferença das concentrações de ácido ascórbico e colesterol da adrenal quando comparadas as duas intensidades de exercício (M e S) (P < 0,05). CONCLUSÃO: Todos os biomarcadores do eixo HHA apontaram alterações no nível de estresse de ratos submetidos a exercício agudo de natação; as concentrações séricas de ACTH e corticosterona mostraram-se mais sensíveis a pequenas alterações na intensidade do exercício.

INTRODUCTION: The level of stress during acute/chronic exercise is important, since higher levels of stress may impair animal welfare. The adrenocorticotrophic (ACTH) and corticosterone hormone concentrations, as well as cholesterol and ascorbic acid concentrations in adrenal gland, are considered an important stress biomarker. PURPOSE: To analyze the sensitivity of the different biomarkers during acute swimming exercise in different intensities performed by rats. METHODS: Male Wistar adult rats (n = 18) previously adapted to swimming were submitted to three 25 min. swimming tests with loads of 5.0; 5.5 and 6.0 percent of their body weight (BW), for maximum lactate steady state (MLSS) determination. After MLSS attainment, the animals were divided into two groups: M (n = 9) sacrificed shortly after a 25 min. session of exercise at the MLSS intensity or S (n = 9) sacrificed after exhaustive exercise at intensity 25 percent above MLSS. For comparison purposes, a control group C (n = 10) was sacrificed in rest. RESULTS: Serum ACTH and corticosterone concentrations were higher after exercise for the two groups (M and S) when compared with control group C (P < 0.05). The group S presented higher concentrations for both hormones in relation to the group M (P < 0.05). The concentrations of the cholesterol and ascorbic acid in adrenal were lower after exercise for the two groups (M and S) when compared with control group C (P < 0.05). No significant differences in adrenal ascorbic acid and cholesterol levels were observed when the two exercise intensities (M and S) were compared (P < 0.05). CONCLUSION: All biomarkers of HPA activity pointed alterations in the stress level of the rats submitted to acute swimming exercise. ACTH and corticosterone serum concentrations showed to be more sensitive to small alterations in the effort intensity.

Máxima fase estável de lactato é ergômetro-dependente em modelo experimental utilizando ratos / The maximal lactate steady state is ergometer-dependent in experimental model using rats

A máxima fase estável de lactato (MFEL) é considerada padrão-ouro para a determinação da intensidade de transição metabólica aeróbia-anaeróbia em exercício contínuo, porém a resposta lactacidêmica nessa intensidade é, em humanos, dependente do ergômetro utilizado na avaliação. Uma ferramenta importante para estudos em fisiologia e áreas correlatas é a aplicação de modelos experimentais utilizando animais. Entretanto, ainda são restritas as pesquisas destinadas a investigar protocolos de avaliação em ratos. O objetivo do estudo foi verificar se a MFEL é dependente do ergômetro utilizado para a avaliação aeróbia de ratos. Para isso, 40 ratos Wistar adultos foram avaliados em dois diferentes exercícios: natação e corrida em esteira. Em ambos, a MFEL foi verificada após aplicação de quatro testes contínuos, em diferentes intensidades, com duração de 25 minutos, separados por intervalo de 48 horas. Em todos os testes houve coleta sanguínea da cauda dos animais a cada cinco minutos de exercício para análise do lactato sanguíneo. Os testes de natação ocorreram em tanque cilíndrico profundo, com a temperatura da água a 31 ± 1°C. As cargas adotadas para os testes foram de 4,5; 5,0; 5,5; 6,0 por cento do peso corporal, atadas ao dorso dos animais. Para a determinação da MFEL em corrida, houve seleção dos ratos corredores e as velocidades dos testes foram de 15, 20, 25, 30m.min¹. A MFEL foi interpretada como a mais alta intensidade de exercício na qual o aumento da lactacidemia foi igual ou inferior a 1mM, do 10° ao 25° minuto. Anova one-way identificou diferenças entre as concentrações de lactato sanguíneo nos diversos tempos de exercício e ergômetros. A MFEL na natação ocorreu a 5,0 por cento do peso corporal (pc), em concentração de lactato de 5,20 ± 0,22mM. Para o exercício em esteira rolante, observou-se MFEL a 20m.min¹, em concentração 3,87 ± 0,33mM. Dessa forma, é possível concluir que a MFEL também é ergômetro-dependente...

The maximal lactate steady state (MLSS) is considered the gold standard method for determination of aerobic/anaerobic metabolic transition during continuous exercise, but the blood lactate response at this intensity is ergometer-dependent in human beings. An important tool for exercise physiology and correlated fields is the use of animal models. However, investigation on evaluation protocols in rats is scarce. The aim of the present study was to verify if the MLSS is ergometer-dependent for the evaluation of the aerobic conditioning of rats. Therefore, 40 adult male Wistar rats were evaluated in two different exercise types: swimming and treadmill running. In both, the MLSS was obtained with 4 continuous 25 minutes tests, at different intensities, performed at 48 hours intervals. In all tests, blood samples were collected from a cut at the tail tip every 5 minutes for blood lactate analysis. The swimming tests occurred in a deep cylindrical tank, with water temperature at 31 ± 1°C. The loads used in the tests were 4.5; 5.0; 5.5 and 6.0 percent of the body weight tied to the animal's back. For MLSS determination in running exercise, there was selection of running rats and velocities used in the tests were 15, 20, 25, 30 m.min-1. The MLSS was interpreted as an increase not exceeding 1.0 mM of blood lactate, from the 10th to the 25th minute of exercise. The MLSS in swimming exercise occurred at 5.0 percent of body weight (bw), with blood lactate at 5.20 ± 0.22 mM. The running rats presented MLSS at the 20 m.min-1 velocity, with blood lactate of 3.87 ± 0.33 mM. The results indicated that the MLSS is ergometer-dependent in experimental models using animals, as it is in human beings.

La máxima fase de estabilidad de lactato (MFEL) es considerada oro padrón para la determinación de la intensidad de transición metabólica aerobia-anaerobia en ejercicio continuo, sin embargo la respuesta lactacidémica en esa intensidad es, en humanos, dependiente del ergómetro utilizado en la evaluación. Una herramienta importante para estudios en fisiología y áreas correlacionadas es la aplicación de modelos experimentales utilizando animales. Entretanto, todavía son restrictas las investigaciones destinadas a investigar protocolos de evaluación en ratones. El objetivo del presente estudio ha sido el de verificar si MFEL es dependiente del ergómetro utilizado para la evaluación aerobia de ratones. Para eso, 40 ratones Wistar adultos fueron evaluados en dos diferentes ejercicios: natación y carrera en faja ergo métrica. En ambos, la MFEL fue verificada después de la aplicación de 4 tests continuos, en diferentes intensidades, con duración de 25 minutos, separados por intervalos de 48 horas. En todos los tests hubo colecta sanguínea de la cola de los animales a cada 5 minutos de ejercicio para analizar el lactato sanguíneo. Los tests de natación ocurrieron en un tanque cilíndrico profundo, con el agua a temperatura de 31 ± 1°C. Las cargas adoptadas para los tests fueron 4,5; 5,0; 5,5; 6,0 por ciento del peso corporal, atadas al dorso de los animales. Para la determinación de la MFEL en carreras, hubo una selección de los ratones corredores y las velocidades de los tests fueron de 15, 20, 25, 30 m.min-1. La MFEL fue interpretada como la más alta intensidad de ejercicio en la que el aumento de lactacidemia fue igual o inferior a 1mM, del 10° al 25° minuto. Anova one-way identificó diferencias entre las concentraciones de lactato sanguíneo en los diversos tiempos de ejercicio y ergómetros. La MFEL en la natación ocurrió a 5,0 por ciento pc, en concentración de lactato de 5,20 ± 0,22 mM. Para el ejercicio en faja...