| Objective: Extensive soft tissue injury, especially the contusion of both buttock and lower extremities is common in forensic practice. It is characteristic of the local crush injuries which seem slight, however, induce severe secondary injuries of system and exacerbate dysfunctions of remote organs such as lung and liver which develop rapidly and secretly, often resulting in irreversible and lethal multiple organ dysfunction syndrome (MODS). With the development of crush injury model in our laboratory, it was revealed that the anti-oxidant capacity in lung, liver and kidney significantly decreased in crushing hind-limbs of rabbits, and pro-inflammatory cytokines such as TNF-α and IL-1 β were involved in this process. Nitric oxide (NO) is a novel gas signal molecule and plays a variety of regulations for physiology. At the meanwhile it belongs to free radical according to its chemical structure and active character which confer its beneficial and detrimental roles in a lot of physiologic and patho-physiologic processes depended on the discrepancies of dose, action interval of NO and the differences of target organs of NO. So NO is also known as a double-edged sword. NO is product of oxygenation ofL-arginine catalyzed by the isoforms of enzymes labeled as nitric oxide synthase (NOS). In general, NOS was catalogued into two main types of constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS). It is well known that trauma,profound stress and pro-inflammatory cytokines can elicit the induction of expression of iNOS mRNA and the regulation for cNOS activity, as well as alterations of NO production and functions. Up to now, it is unknown that changes and roles of NO, and NOS in local injury of muscle and secondary injury of remote organs such as lung and liver caused by crushing hind limbs of rats. In this study, we tried to examine the involvement of NO and NOS changes in the development of local injury of muscle and acute lung and liver injury under the experimental model of crush injury induced by exertion of standardized mechanical pressure. Methods: Fifty-five healthy wistar rats, either female or male, weighed between 160±20g, were used in this study. With an apparatus designed for this experiment , rat was fixed down- ward on the wood stand. Then the hind limbs of rat were subjected to the same standardized external mechanical pressure of 15 kilogram to induce crush injury for 5 hours. Then the rat was released and acted freely. After another 5 hours rats were anesthetized by 5% pentobarbital sodium (30 mg/kg bw) intra-peritoneally and had laparotomy. From abdominal aorta blood was taken before rat was exanguinatedto death. The samples of local muscle of hind limbs, lung and liver were collected and restored for further study. Rats were randomly divided into (1) sham group, (2) crush group, (3) crush + aminoguanidine group, and (4) crush + L-arginine group, short for S group, C group, A group, and L group, respectively. Rats in S group were treated as C group except for without crushing the hind limbs of rats. Rats in C group were treated in accord as above-mentioned mode for crushing the hind limbs of rats. Rats in A group and L group were treated as C group, together with the injection of a selective iNOS inhibitor aminoguanidine (AG, 10 mg/kg bw) and NOS substrate L-arginine (L-Arg, 150 mg/kg bw) through sublingual vein, respectively. This experiment contained two parts. The first part, was designed to investigate the relationship of changes of NO content, NOS activity, both iNOS and eNOS protein expression in local muscle to the secondary damage to crushed local muscle.The second one was carried out to investigate the role of changes of NO content, NOS activity, both iNOS and eNOS protein expression in liver and lung in the acute lung injury and liver injury induced by crushing hind limbs of rat. NO content and NOS activity were measured spectrophotometrically, iNOS and eNOS protein expression was detected with immuno- histochemistry tec...
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