ABSTRACT
BACKGROUND: Ischemic postconditioning protects the myocardium from ischemia/recursion injury via maintaining 3-minute acidosis initially. But its effect on the skeletal muscle remains unclear. OBJECTIVE: To dynamically measure the pH values in rat skeletal muscle after ischemia, and then to simulate acidic perfusate infusion to investigate the effect of ischemic postconditioning on ischemia/reperfusion injury. METHODS: Based on the ischemia/reperfusion injury model and ischemic postconditioning protocol in previous study, dynamic measurement of pH values in rat skeletal muscle was conducted using pH instrument at the global ischemia, ischemic postconditioning (30/30 seconds) and reperfusion period, and then the acidic perfusate equivalent to pH in ischemic postconditioning period was prepared with lactic acid and normal saline. Twenty-five healthy adult male Sprague-Dawley rats were randomly divided into sham, ischemia/reperfusion, ischemic postconditioning, lactic acid, and normal saline groups (n=5 per group). Blood samples were collected to detect lactate dehydrogenase level. The samples from gastrocnemius were harvested to calculate the wet/dry ratio, level of myeloperoxidase, and infarct size through triphenyltetrazolium chloride staining. The samples from the right tibialis anterior muscle were taken to detect the expression level of Erk1/2 in the MAPK signaling pathway by western blot assay. RESULTS AND CONCLUSION: A prolonged acidic platform was detected in the early reperfusion during ischemic postconditioning, on which the pH value was 6.81±0.133, and the duration was 2 minutes and 40 seconds. The levels of lactate dehydrogenase and myeloperoxidase as well as the wet/dry ratio in the ischemic postconditioning and lactic acid groups were significantly lower than those in the ischemia/reperfusion group (P < 0.05). Western blot assay results showed that the expression level of p-Erk in the ischemic postconditioning, lactic acid and normal saline groups was significantly higher than that in the ischemia/reperfusion group (P < 0.05). Triphenyltetrazolium chloride staining results showed that compared with the ischemia/reperfusion group, the infarct area was significantly reduced in the postconditioning and lactic acid groups (P < 0.05). These findings suggest the existence of a short acidosis during ischemic postconditioning in the early reperfusion, and acidic perfusate can simulate the ischemic postconditioning and effectively attenuate ischemia/reperfusion injury in the rat skeletal muscle via activating Erk1/2 in RISK signaling pathway.
ABSTRACT
BACKGROUND:Reperfusion injury salvage kinase (RISK) pathway plays an important role in protective mechanism against ischemia reperfusion injury (IRI) induced by both ischemic pre-and post-conditioning. Many researches have been carried out on RISK pathway mechanism underlying ischemic post-conditioning conferring cardioprotection against IRI;however, there is less research about its effect on IRI in the skeletal muscle. OBJECTIVE:To investigate the protective effect of an optimized protocol of ischemic post-conditioning on IRI in rat skeletal muscle and its underlying mechanism. METHODS:Eighteen male Sprague-Dawley rats were equivalently randomized into IRI, ischemic post-conditioning and control groups. Rats were given occlusion or disocclusion of the right femoral artery of the right lower limb. Subsequently, the IRI group rats were subjected to 24 hours of reperfusion;the ischemic post-conditioning group immediately given 4 cycles of 30 seconds reperfusion/30 seconds ischemia, followed by 24 hours of reperfusion;the control group given no intervention. RESULTS AND CONCLUSION:Hematoxylin-eosin staining showed that in the ischemic post-conditioning group, the morphology of muscle fibers changed little, with fewer inflammatory lesions and milder edema compared with the IRI group. The infarct size with TTC staining in the ischemic post-conditioning group was smaller than that in the IRI group. Western blot analysis revealed that the expressions of phospho-Akt and phosphorylated endothelial nitric oxide synthase-S1177 were significantly increased, but the expression of phosphorylated type endothelial nitric oxide synthase-Thr495 was much decreased in the ischemic post-conditioning group compared with the IRI group. The measurement of mitochondrial permeability transition pore opening with Ca2+induction showed that the absorbance values in the ischemic post-conditioning group were significantly lower than those in the IRI group (P<0.05). These results indicate that ischemia-reperfusion injury can be improved by applying an optimal protocol of ischemic post-conditioning in rat skeletal muscle. The underlying mechanism may be associated with the activation of RISK signaling pathway to inhibit opening of mitochondrial permeability transition pore, thereby contributing to the enhanced tolerance to IRI in rat skeletal muscle.
ABSTRACT
The scientific indexes and methods for checking utilization and intact rates of analytical instruments are established by cybernetic principles, fozzy mathemetical mdthods, theories of systematic engineering, and actual conditions of working units. it is proved that the realization of scientific management and control to manipulators, instruments and working enviroment can raise the utilization and intact rates of analytical instruments, guarantee the assay quality of drugs, increase the efficiency of supervision and promote the research work in drug analysis. Definite social and economic results are thus obtained.