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Rehn TA, Borge BA, Lunde PK, Munkvik M, Sneve ML, Gr&3x00F8;ndahl F, Aronsen JM, Sjaastad I, Prydz K, Kolset SO, Wiig H, Sejersted OM, Iversen P0. Temporary fatigue and altered extracellular matrix in skeletal muscle during progression of heart failure in rats. Am J Physiol Regul Integr Comp Physiol 297: R26-R33, 2009. First published April I, 2009; doi:l0.l 152/ajpregu.906l7.2008.-Patients with congestive heart failure (CHF) experience increased skeletal muscle fatigue. The mechanism underlying this phenomenon is unknown, but a deranged extracellular matrix (ECM) might be a contributing factor. Hence, we examined ECM components and regulators in a rat postinfarction model of CHF. At various time points during a 3.5 mo-period after induction of CHF in rats by left coronary artery ligation, blood, interstitial fluid (IF), and muscles were sampled. Isoflurane anesthesia was employed during all surgical procedures. IF was extracted by wicks inserted intermuscularly in a hind limb. We measured cytokines in plasma and IF, whereas matrix metalloproteinase (MMP) activity and collagen content, as well as the level of glycosaminoglycans and hyaluronan were determined in hind limb muscle. In vivo fatigue protocols of the soleus muscle were performed at 42 and 112 days after induction of heart failUre. We found that the MMP activity and collagen content in the skeletal muscles increased significantly at 42 days after induction of CHF, and these changes were time related to increased skeletal muscle latigability. These parameters returned to sham levels at 112 days. VEGF in IF was significantly lower in CHF compared with sham-operated rats at 3 and 10 days, but no difference was observed at 112 days. We conclude that temporary alterations in the ECM, possibly triggered by VEGF, are related to a transient development of skeletal muscle fatigue in CHF. [ABSTRACT FROM AUTHOR]