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BACKGROUND: The biochemical and metabolic role played by nitric oxide (NO) in course of oxidative stress due to cell hypoxia, ischemia and reperfusion has a determinant relevance in the mitochondrial adaptive changes which antagonize the irreversible morpho-functional damage. In particular conditions, such as in prolonged ischemia and/or exogenous NO supplementation, this element is present in the radical form (NOO*) concurring to peroxidative cell injury. Aim of this study was to investigate these opposite NO aspects in hypoxic, ischemic and reperfused human skeletal muscle tissue. METHODS: Skeletal muscle samples were taken during elective knee orthopedic surgery in 10 consecutive patients. The biopsies were obtained before, after 5+/-1 min and 58+/-2 min from tourniquet application and then after 18+/-3 min following muscle reperfusion. The samples, immediately frozen in liquid nitrogen, were assayed for endocellular free NO following the gas-amperometric method described by Palmerini C. RESULTS: When compared with normoxic tissues, a significant decrease in free NO content was observed in hypoxic samples. After about 60 min of prolonged ischemia the NO levels show an evident increase, while the tissue reperfusion leads to a progressive restoration of physiological content in the cellular free nitric oxide. CONCLUSIONS: The obtained data in hypoxic muscle cell seem to underline the pivotal role played by NO in adapting the cytochrome c oxidase oxidative activity to lower O2 bio-availability. On the other hand the prolonged ischemia leads to a consistent NOO* generation triggered by oxyradical generation and Ca2+ intracellular over load. Even if the tissue reoxygenation restores the normal NO levels it is arguable that the pre-treatment of ischemic cell with antioxidants, Ca-antagonist and Dexamethasone supplementation could represent a crucial and specific therapeutic approach to critically ill patient.

BACKGROUND: Following our previous studies on the biomolecular and biochemical aspects of the human tissue oxidative damage due to hypoxia, ischemia and reperfusion, aim of the present work is to evaluate the role played by oxyradical generation in the morphofunctional cellular injury. We evaluated the tissue levels of some metabolic markers (MDA, Catalase, Uric Acid) to obtain a pathogenic picture and then a therapeutic approach closely related to the cellular biodynamics. METHODS: A skeletal muscle samples were taken during elective knee orthopedic surgery in 20 consecutive patients. The biopsies were taken in normoxic conditions and after 5 +/- 1 and 62 +/- 3 min form tourniquet application and finally 21 +/- 2 min following muscle reperfusion. The samples were assayed for tissue Malondialdeyade (MDA), uric acid and catalase (CAT) contents with HPLC and fluorimetric procedures. All data were evaluated in terms of computerized statistical analysis. RESULTS: When compared to normoxic tissue (1.24 +/- 0.26 nmoli.mg-1 protein), the MDA levels show a moderate increase in hypoxic (1.66 +/- 0.12) and ischemic tissue (1.78 +/- 0.13), while highly significant is the rise in reperfused muscle MDA content (5.94 +/- 0.15). The uric acid as far as CAT shows no appreciable alterations in hypoxia and ischemia. Following reoxygenation an increase in uric acid contents with a concomitant CAT tissue consumption appear evident. CONCLUSIONS: The obtained data seem to underline the cytoprotective role played by adaptive changes in the hypoxic and ischemic human cells. On the contrary, the rapid reoxygenation of the ischemic tissue appears to start oxyradical neo-generation. In clinical and therapeutic terms these observations underline a peculiar and different approach to the critically ill patient.