Effects of a Single Bout of Resistance Exercise in Different Volumes on Endothelium Adaptations in Healthy Animals / Efeitos de uma Sessão de Exercício Resistido em Diferentes Volumes sobre Adaptações Endoteliais em Animais Saudáveis

Abstract Background: Resistance exercise (RE) has been recommended for patients with cardiovascular diseases. Recently, a few studies have demonstrated that the intensity of a single bout of RE has an effect on endothelial adaptations to exercise. However, there is no data about the effects of different volumes of RE on endothelium function. Objective: The aim of the study was to evaluate the effects of different volumes of RE in a single bout on endothelium-dependent vasodilatation and nitric oxide (NO) synthesis in the mesenteric artery of healthy animals. Methods: Male Wistar rats were divided into three groups: Control (Ct); low-volume RE (LV, 5 sets x 10 repetitions) and high-volume RE (HV, 15 sets x 10 repetitions). The established intensity was 70% of the maximal repetition test. After the exercise protocol, rings of mesenteric artery were used for assessment of vascular reactivity, and other mesenteric arteries were prepared for detection of measure NO production by DAF-FM fluorescence. Insulin responsiveness on NO synthesis was evaluated by stimulating the vascular rings with insulin (10 nM). Results: The maximal relaxation response to insulin increased in the HV group only as compared with the Ct group. Moreover, the inhibition of nitric oxide synthesis (L-NAME) completely abolished the insulin-induced vasorelaxation in exercised rats. NO production showed a volume-dependent increase in the endothelial and smooth muscle layer. In endothelial layer, only Ct and LV groups showed a significant increase in NO synthesis when compared to their respective group under basal condition. On the other hand, in smooth muscle layer, NO fluorescence increased in all groups when compared to their respective group under basal condition. Conclusions: Our results suggest that a single bout of RE promotes vascular endothelium changes in a volume-dependent manner. The 15 sets x 10 repetitions exercise plan induced the greatest levels of NO synthesis.

Resumo Fundamentos: O exercício resistido (ER) tem sido recomendado para pacientes com doenças cardiovasculares. Recentemente, alguns estudos demonstraram que a intensidade de uma sessão de ER exerce um efeito sobre a disfunção endotelial. No entanto, não há dados sobre os efeitos de diferentes volumes de ER sobre a função endotelial. Objetivo: O objetivo deste estudo foi avaliar os efeitos de diferentes volumes de ER, realizados em uma única sessão, sobre a vasodilatação dependente do endotélio e síntese de óxido nítrico (NO) em artéria mesentérica de animais saudáveis. Métodos: Ratos Wistar machos foram divididos em três grupos: Controle (Ct); baixo volume (BV, 5 séries x 10 repetições) e alto volume de ER (AV, 15 séries x 10 repetições). Foi estabelecida a intensidade de 70% do teste de repetição máxima. Após o protocolo de exercício, anéis de artéria mesentérica foram utilizados na avaliação da reatividade vascular, e outras artérias mesentéricas foram preparadas para a detecção da produção de NO por fluorescência com para do DAF-FM. A resposta à insulina pela síntese de NO foi avaliada estimulando-se os anéis vasculares com insulina (10nM). Resultados: A resposta máxima do relaxamento induzido por insulina foi aumentada somente no grupo AV em comparação ao grupo Ct. Além disso, a inibição da síntese do NO (L-NAME), aboliu completamente o relaxamento vascular induzido por insulina em ratos exercitados. A produção de NO mostrou um aumento dependente do volume no endotélio e no músculo liso. No endotélio, apenas os grupos Ct e BV mostraram aumento significativo na síntese de NO quando comparado aos seus respectivos grupos sob condição basal. No entanto, no músculo liso, a fluorescência foi aumentada em todos os grupos quando comparados aos seus respectivos grupos sob a condição basal. Conclusões: Nossos resultados sugerem que uma única sessão de ER foi capaz de promover adaptações no endotélio vascular. Além disso, nós observamos que este efeito é volume-dependente e o volume de 15 séries x10 repetições induziu o maior aumento na síntese de NO.

Ischemia-reperfusion histopathology alterations of the rabbit intestinal wall with and without exclusion of the collateral mesenteric circulation supply / Alterações histopatológicas da parede intestinal de coelhos na isquemia-reperfusão com e sem exclusão da circulação mesentérica colateral

PURPOSE: To evaluate the histopathology alterations of the intestinal mucosa of rabbits submitted to different times of mesenteric artery ischemia and reperfusion with and without celiac artery collateral circulation supply. METHODS: Two groups of eight male New Zealand white rabbits (weight 2.2-3.5 kg) were used in this study. In the Group 1 animals, the proximal mesenteric artery was occluded for 60 min with an atraumatic vascular clamp, followed by reperfusion for 60 min. In the Group 2 animals the small bowel and mesentery were cut 30cm and 60cm far from the gastroduodenal pyloric transition before the proximal mesenteric artery occlusion. Small bowel biopsies were obtained before ischemia (control), after 30 min and 60 min of mesenteric ischemia and at 30 and 60 min. of mesenteric artery reperfusion. RESULTS: In the Group I animals, the followings histopathology grade results were observed: t1, mean 0.4 + 0.29; t2, mean 1.9 ± 0.38; t3, 1.9 ± 0.33; t4, 1.2 ± 0.36 and t5, 1.2 ± 0.32. Differences between t0 and t2 and between t3 and t4 were statistically significant (p<0.05). Differences between t2 and t3 and t4 and t5 were not significant (p>0.5). In the Group II animals, it was observed: t1, mean 1.6 ± 0.33; t2, 2.4 ± 0.36; t3, 3.0 ± 0.35; t4 3.4 ± 0.31; t5, 3 ± 031. Differences between t0 and t1, t1 and t2, and t2 and t3 were significant (p<0.05). Differences between histopathology grades results of samples t1 to t5 in Group 1 and 2 were statistically significant (p<0.5). CONCLUSION: Microscopic examination of the biopsies revealed significant evidence of worse small bowel wall ischemia-reperfusion lesions by exclusion of the celiac artery collateral circulation supply.

OBJETIVO: Avaliar as alterações histopatológicas da mucosa intestinal de coelhos submetidos à isquemia-reperfusão com e sem exclusão da circulação mesentérica colateral. MÉTODOS: Foram estudados dois grupos de oito coelhos Nova Zelândia machos com pesos variáveis entre 2,2 e 3,5 kg de peso corpóreo. Nos animais do Grupo 1, a artéria mesentérica proximal foi ocluida por pinçamento atraumático durante 60 min, seguido de reperfusão por 60 min. No Grupo 2 o intestino delgado e o mesentério foram seccionados 30 cm e 60 após a transição pilórica gastroduodenal antes da oclusão da artéria mesentérica cranial. Biópsias da parede intestinal foram obtidas antes da isquemia (controle), após 30 e 60 min. de isquemia. RESULTADOS: No Grupo I foram observados os seguintes graus de lesões: t1,média de 0.4 + 0.29; t2, média 1.9 ± 0.38; t3, 1.9 ± 0.33; t4, 1.2 ± 0.36 e t5, 1.2 ± 0.32. As diferenças entre t0 e t2 e entre t3 e t4 foram significantes (p<0.05). As diferenças entre t2 e t3 e t4 e t5 não foram significantes (p>0.5). No Group II observou-se: t1, média de 1.6 ± 0.33; t2, 2.4 ± 0.36; t3, 3.0 ± 0.35; t4 3.4 ± 0.31; t5, 3 ± 031. As diferenças entre t0 e t1, t1 e t2, e t2 e t3 foram significantes (p<0.05). As diferenças entre os resultados histopatológicos das biopsies de t1 a t5 dos Grupos 1 e 2 foram significantes (p<0.5). CONCLUSÃO: A exclusão da circulação mesentérica colateral agravou significantemente a degeneração histopatológica na isquemia-reperfusão da parede intestinal.

A key role for Na+/K+-ATPase in the endothelium-dependent oscillatory activity of mouse small mesenteric arteries

Oscillatory contractile activity is an inherent property of blood vessels. Various cellular mechanisms have been proposed to contribute to oscillatory activity. Mouse small mesenteric arteries display a unique low frequency contractile oscillatory activity (1 cycle every 10-12 min) upon phenylephrine stimulation. Our objective was to identify mechanisms involved in this peculiar oscillatory activity. First-order mesenteric arteries were mounted in tissue baths for isometric force measurement. The oscillatory activity was observed only in vessels with endothelium, but it was not blocked by L-NAME (100 µM) or indomethacin (10 µM), ruling out the participation of nitric oxide and prostacyclin, respectively, in this phenomenon. Oscillatory activity was not observed in vessels contracted with K+ (90 mM) or after stimulation with phenylephrine plus 10 mM K+. Ouabain (1 to 10 µM, an Na+/K+-ATPase inhibitor), but not K+ channel antagonists [tetraethylammonium (100 µM, a nonselective K+ channel blocker), Tram-34 (10 µM, blocker of intermediate conductance K+ channels) or UCL-1684 (0.1 µM, a small conductance K+ channel blocker)], inhibited the oscillatory activity. The contractile activity was also abolished when experiments were performed at 20°C or in K+-free medium. Taken together, these results demonstrate that Na+/K+-ATPase is a potential source of these oscillations. The presence of α-1 and α-2 Na+/K+-ATPase isoforms was confirmed in murine mesenteric arteries by Western blot. Chronic infusion of mice with ouabain did not abolish oscillatory contraction, but up-regulated vascular Na+/K+-ATPase expression and increased blood pressure. Together, these observations suggest that the Na+/K+ pump plays a major role in the oscillatory activity of murine small mesenteric arteries.

Breast milk versus infant formulas: effects on intestinal blood flow in neonates.

The differences between breast milk and infant formulas have been a popular subject of many recent studies. Most concern the chemical and biological characteristics of breast milk and infant formulas, but little work has been done about hemodynamic changes in the splanchnic circulation. In term neonates (n = 22) we evaluated the effect of breast milk, adapted cow's milk formula, and nucleotide supplemented cow's milk formula on intestinal blood flow. To determine the blood flow velocity and estimate volume flow, pulsed Doppler ultrasound of the superior mesenteric artery (SMA) was performed prefeeding and 15, 45, and 90 minutes following feeding. When pre- and postprandial blood flow features of babies were compared among in their groups according to nutrition post prandial blood flow velocity and volume flow were increased significantly over baseline in all three groups. While there was no significant difference between the postprandial blood flow parameters of the breast milk and adapted cow's milk formula-fed groups, the nucleotide supplemented cow's milk formula-fed group had significantly higher postprandial blood flow velocity and volume flow.