Heart failure (HF) is characterized by a reduced tolerance to exercise due to early fatigue and dyspnea; this may be due in part to skeletal muscle myopathy with a shift from slow to fast fibers and loss of muscle mass. Muscle wasting does not occur similarly in all types of muscle fiber, thus we tested the hypothesis that HF induces skeletal muscle atrophy in a fiber type-specific manner altering the expression of atrogin-1 and MuRF1 in a fast muscle of rats with monocrotaline-induced heart failure. We studied extensor digitorum longus (EDL) muscle from both HF and control Wistar rats. Atrogin-1 and MuRF1 mRNA content were determined using Real-Time RT-qPCR while muscle fiber cross-sectional area (CSA) from sections stained histochemically for myofibrillar ATPase were used as an index of type-specific fiber atrophy. The measurement of gene expression by RT-qPCR revealed that EDL muscle mRNA expression of MuRF1 and atrogin-1 was significantly increased in the HF group. Muscle fiber type IIB CSA decreased in the HF group compared to the CT group; there was no significant difference in muscle fiber types I and IIA/D CSA between the HF and CT groups. In conclusion, we showed that HF induces fiber type IIB specific atrophy, up-regulating atrogin-1 and MuRF1 mRNA expression in EDL muscle of monocrotaline treated rats.
Heart failure (HF) is characterized by limited exercise tolerance, skeletal muscle atrophy, a shift toward fast muscle fiber, and myogenic regulatory factor (MRF) changes. Reactive oxygen species (ROS) also contribute to target organ damage in this syndrome. In this study, we investigated and compared morphofunctional characteristics and gene expression in Soleus (SOL--oxidative and slow twitching muscle) and in Extensor Digitorum Longus (EDL--glycolytic and fast twitching muscle) during HF. Two groups of rats were used: control (CT) and heart failure (HF), induced by a single injection of monocrotaline. MyoD and myogenin gene expression were determined by RT-qPCR, and MHC isoforms by SDS-PAGE; muscle fiber type frequency and cross sectional area (CSA) were analyzed by mATPase. A biochemical study was performed to determine lipid hydroperoxide (LH), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD); myography was used to determine amplitude, rise time, fall time, and fatigue resistance in both muscles. HF showed SOL and EDL muscle atrophy in all muscle fiber types; fiber frequency decreased in type IIC and muscle contraction fall time increased only in SOL muscle. Myogenin mRNA expression was lower in SOL and myoD decreased in HF EDL muscle. LH increased, and SOD and GSH-Px activity decreased only in HF SOL muscle. HF EDL muscle did not present changes in MHC distribution, contractile properties, HL concentration, and antioxidant enzyme activity. In conclusion, our results indicate that monocrotaline induced HF promoted more prominent biochemical, morphological and functional changes in SOL (oxidative and slow twitching muscle). Although further experiments are required to better determine the mechanisms involved in HF pathophysiology, our results contribute to understanding the muscle-specific changes that occur in this syndrome.
ResumoO objetivo da pesquisa foi comparar a pressão arterial de profissionais auxiliares de enfermagem em dois momentos distintos durante o trabalho profissional e no momento do descanso do trabalho. Participaram do estudo 31 auxiliares de enfermagem de um hospital de ensino que trabalhavam em regime de 12 horas de trabalho e 36 horas de descanso. Para verificação da pressão arterial foi utilizado o aparelho digital de Medida Residencial da Pressão Arterial (MRPA) de braço devidamente calibrado. Cada profissional recebeu um aparelho de MRPA para utilizá-lo após treinamento, verificando a pressão arterial durante 3 dias de trabalho e 3 dias de descanso em 3 horários pela manhã. Em relação aos sujeitos da pesquisa 80,65% eram do sexo feminino e 19,35% masculino, a faixa etária de maior prevalência foi de 31 a 40 anos. Nenhum participante da pesquisa fumava, relatava uso de álcool ou doenças pré-existentes. Na aplicação do teste t-Student pareado, ao nível de significância de 0,05 não houve evidências de que as médias fossem diferentes. A pressão arterial sistólica (PAS) trabalho foi de 115,55 ± 9,66 mmHg e PAS casa de 114,39 ± 9,10 mmHg e pressão arterial diastólica (PAD) trabalho de 73,97 ± 7,50 mmHg e PAD casa de 72,77 ± 7,88 mmHg. Na avaliação da Freqüência cardíaca (FC), a FC trabalho foi de 83,65 ± 9,50 bpm e FC casa de 79,23 ± 6,92 bpm (p<0,05). Os dados da pesquisa não evidenciam diferença estatística significante entre a pressão arterial nos momentos de trabalho e em casa porém, observamos um aumento significativo da freqüência cardíaca. Palavras-chave: monitoramento, pressão arterial, auxiliares de enfermagem.
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