Abstract: Objective To investigate the change of nitric oxide (NO) level in local muscles induced by crushing hind-limbs in rats. Methods The rat experimental model of hind-limb crushing injury was established by crushing the hind limbs of rats with standard weight for 5 hours, thereafter releving the standard weight for another 5 hours. The rats were randomly divided into sham group, crushing group, crushing and injecting aminoguanidine (AG) group, crushing and injecting L-arginine (L-Arg) group.The NOS activity and NO level in local muscles and serum were spectrophotometrically measured, and iNOS and eNOS protein expressions in local muscles were examined by immunohistochemistry. The weight ratio of wet to dry (W/D) of local muscles was measured and the pathologic changes were observed. Results The crushing hind-limbs induced serious primary and secondary injuries of local muscles such as rupture and rhadomyolysis of skeletal muscular fibers,interstitial vascular congestion and edema,and marked increase in W/D.The expressions of eNOS and iNOS were upregulated in local muscle in crush group compared with sham group.The NOS activity and NO level in local muscles and serum significantly increased. There was positive relationship between NO level and W/D in local muscles. With the usage of AG and L-arg,the hind-limb injuries seemed alleviated and aggravated, respectively. Conclusion The crushing hind-limbs of rats elicited the upregulation of eNOS and iNOS protein expression, the enhancement of NOS activity and the excess production of NO, the latter of which was involved in the mediation of secondary pathological changes in local muscles.

Key words: crush injury, nitric oxide, induciable nitric oxide synthase, endothelial nitric oxide synthase