RESUMO
Objective:To investigate effect of reperfusion injury following different ischemic duration on skeletal muscle in rats.Methods:A model of ischemia/reperfusion injury (IRI) was established by unilateral clamping femoral artery and additional application of tourniquet in skeletal muscle of hind limbs in 35 male Wsitar rats. According to different ischemia time, the animals were assigned to 2-hour ischemia and 24-hour reperfusion (I2R24 group), 2.5-hour ischemia and 24-hour reperfusion (I2.5R24 group), 3-hour ischemia and 24-hour reperfusion (I3R24 group), 4-hour ischemia and 24-hour reperfusion (I4R24 group) and sham group, with 7 rats per group. At the end of reperfusion, gastrocnemious tissues and plasma samples were collected and analyzed. The ratio of wet ∶ dry weight (W/D) was used to measure muscle edema. The assay of 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) was conducted to evaluate muscle viability. HE staining was executed to observe histopathological changes. Immunofluorescence staining was performed to assess the levels of C1q, C3b/c, tissue factor (TF), fibrinogen (FN), bradykinin receptor 1 (BR1), BR2, vascular cell adhesion molecule-1 (VCAM-1), E-selectin, fibrinogen-like protein-2 (FGL-2) and myeloperoxidase (MPO) in muscle tissues. ELISA method was used to determine the concentrations of interferonγ (IFN-γ), interleukin7 (IL-7), IL-18, macrophage inflammatory1α (MIP-1α) and monocyte chemotactic protein 1 (MCP-1) in plasma.Results:With prolongation of ischemia time and subsequent reperfusion, tissue edema became severe gradually. The ratio of W/D was 5.3±0.2, 6.1±0.3, 6.9±0.2, 7.6±0.3 in I2R24, I2.5R24, I3R24 and I4R24 groups, higher than that in sham group (4.5±0.1) (all P<0.01). Muscle viability got decreased gradually. Muscle viability was (62.4±3.5)%, (45.3±3.3)%, (35.4±3.4)%, (27.1±5.9)% in I2R24, I2.5R24, I3R24 and I4R24 groups, lower than that in sham group［(93.8±7.2)%］(all P<0.01). Histopathological changes became aggravated gradually. The most severe group was I4R24 group, with the most severe myocyte injury, interstitial edema and extensive inflammatory infiltration, followed by I3R24, I2.5R24 and I2R24 groups in order. There was normal structure integrity and neatly arranged myocyte in sham group. Meanwhile, levels of C1q, C3b, FN, BR1, VCAM-1, E-selectin and FGL-2 got increased gradually. The highest levels for these factors were seen in I4R24 group, followed by I3R24 group, I2.5R24 group, I2R24 group and sham group in order. The rough ratio of the number of positive MPO cells/total cell number under high lens (×200) were increased gradually, with the highest level in I4R24 group, followed by I3R24 group, I2.5R24 group, I2R24 group and sham group in order. However, expression of TF and BR2 were not altered significantly among the groups. Plasma levels of INF-γ, IL-7, IL-18, MIP-1α and MCP-1 elevated gradually with prolongation of ischemia time (all P<0.01). The sequence was the sham group, I2R24 group, I2.5R24 group, I3R24 group and I4R24 groups for levels of these factors from low to high (all P<0.01). Conclusion:Reperfusion after prolongation of ischemia duration can increase the activation of complement, coagulation, kinin and endothelial cells as well as the release of inflammatory factors, and thus aggravate the degree of skeletal muscle tissue injury.