Effects of Continuous and Accumulated Exercise on Endothelial Function in Rat Aorta

Abstract

Background:: The practice of exercise in short bouts repeated throughout the day may be an alternative strategy to lift people out of physical inactivity.

Objective:: to evaluate if accumulated exercise, as occurs in continuous exercise training, improve endothelial function in rat aorta.

Methods:: Wistar male rats were divided into three groups: continuous exercise (CEx, 1 hour on the treadmill) or accumulated exercise (AEx, 4 bouts of 15 minutes / day) for 5 days/week for 8 weeks, or sedentary (SED). During the training period, body weight gain and increase in exercise performance were recorded. On sacrifice day, aorta was dissected into rings (3-5 mm) and mounted on the organ bath.

Results:: Fitness was significantly greater in CEx and AEx rats as compared with SED animals. In addition, compared with the SED group, CEx animals had a lower body mass gain, and the aorta obtained from these animals had reduced contractile response to norepinephrine and greater acetylcholine-induced relaxation. These results were not observed in ACEx animals.

Conclusions:: Both CEx and AEx improved fitness, but only CEx led to reduced body weight gain and improved endothelial function.

Fundamento:: A prática de exercícios em sessões curtas que se repetem ao longo do dia pode ser uma alternativa para tirar as pessoas da inatividade física.

Objetivo:: Verificar se o exercício acumulado, tal como ocorre com o treinamento com exercício contínuo, melhora a função endotelial na aorta de ratos.

Métodos:: Ratos Wistar machos foram divididos em 3 grupos: treinamento com exercício contínuo (ExC; 1 hora em esteira) ou com exercício acumulado (ExA; 4 sessões de 15 minutos ao longo do dia) por 5 dias/semana, durante 8 semanas, ou grupo sedentário (SED). Durante o treinamento, foram registrados o ganho de peso corporal e desempenho na esteira. No dia do sacrifício, anéis (3-5 mm) da aorta foram obtidos e montados em banho de órgãos.

Resultados:: Animais ExC e ExA mostraram aptidão física significativamente maior em comparação com os SED. Paralelamente, em comparação com SED, animais ExC tiveram menor ganho de massa corporal, e aortas retiradas desses animais mostraram respostas contrácteis à noradrenalina reduzidas e maior relaxamento induzido pela acetilcolina. Esses resultados não foram observados no grupo ExA.

Conclusões:: Tanto o ExC quanto o ExA melhoraram a aptidão física, mas somente o ExC foi capaz de reduzir o ganho de peso corporal dos animais e melhorar a função endotelial.

Figure 1

Performance gain (%) of animals submitted to continuous exercise training (CEx; A) or accumulated exercise (AEx; B) in comparison to sedentary animals (SED). Columns represent mean ± SEM; in parenthesis, number of independent determinations. *** p < 0.001 compared to SED animals (unpaired Student's t-test).

Figure 2

Concentration-response curves to norepinephrine determined in intact thoracic aorta preparations obtained from animals trained by continuous (ExA) or accumulated exercise (ExA), in comparison to sedentary animals (SED), not treated (A and B) or treated with 10^-4 mol/L L-NAME (C and D) as well as in not treated endothelium denuded thoracic aorta preparations (E and F). In parentheses, the number of independent determinations (n) followed by pEC50 values. Data in mean ± SEM. * p < 0.05 compared with the SED group ("t" test of Student).

Figure 3

Relaxation induced by acetylcholine (ACh; 10^-4 mol/L), in % of phenylephrine-induced pre-contraction (Phe; 10^-5 mol/L), in animals submitted to continuous exercise (ExC; A) or accumulated exercise (ExA; B) training, in comparison with sedentary animals (SED). Columns represent mean ± SEM; in parenthesis, number of independent determinations. *p < 0.05 compared to the SED animals (unpaired Student's t-test).