Objective: To determine the role of hemoglobin(HB) -induced heme oxygenase- 1 ( HO- 1 ) in injured lungscaused by limb ischemia-reperfusion (I/R) in rats.Methods: A rat model of ischemia in the hind limbswas made by clamping the infrarenal aorta with amicrovascular clip, and lung injury occurred afterreperfusion. To induce the expression of HO-1 in the lungs,Hb was administrated intraperitoneally at 16 hours beforereperfusion. Northern blotting and Western blotting wereused to detect the expression of HO-1 in the lungs, and thecarboxyhemoglobin (COHb) level in arterial blood wasassayed. The effect of hemoglobin (Hb) on the injuredlungs after limb I/R was determined by measuring thechanges of lung histology, polymorphonuclear (PMN)count, malondialdehyde (MDA) content and wet-to-dryweight ratio (W/D). Zinc protoporphyrin (ZnPP), aninhibitor of HO, was used to determine whether HO-1 wasinduced by Hb after lung injury.Results: Hb led to a significant increase in HO-1mRNA and protein expression in the lungs, accompanied bythe increase of COHb level in arterial blood. Comparedwith the sham controls, the lung PMN count, MDA contentand W/D significantly increased at 4 hours after limb I/R,which reversed by the pretreatment with Hb at 16 hoursbefore reperfusion. ZnPP blocked this protective role of Hbin the injured lungs.Conclusions: Hb can induce the lung HO-1expression, which plays an important role in the defenseagainst I/R-induced lung injury in rats.

Objective:　To observe the change of nitric oxide (NO) levels in the blood and the morphological change of the muscles in the limbs of rats during the (IR) injury and after being intervened by L-arginine (L-Arg) and L-nitroarginine (L-NNA).　　Methods:　Sixty-six male Sprague-Dawley (SD) rats were used and grouped into the normal controls, the sham injury controls, the IR injury group and the intervention groups (L-Arg group and L-NNA group). After 6 hours of ischemia, followed by reperfusion for 3, 12 or 24 hours, the samples in the IR injury group were obtained. The rats in the intervention groups were given L-Arg (100 mmol/L) and L-NNA (10 mmol/L), respectively, through the abdominal cavity. Then the anterior tibial muscle in the right limb was obtained for histological examination, the anterior tibial muscle in the left limb for ultrastructure observation and the blood for assay of NO in all the rats. NO was assayed by indirect measurement of NO2/NO3 with Griess method. 　　Results:　There was no significant difference of NO between the normal controls and the sham injury controls (P>0.05). But NO significantly decreased in the IR injury group (P<0.01), and further decreased with reperfusion (P<0.01) and reached the lowest point at 12 hours after reperfusion. The level of NO in the L-Arg group was significantly higher than that in the IR injury group (P<0.01), but was not significantly different from that in the controls (P>0.05). In the L-NNA group, NO decreased to the undetectable level (P<0.01). Histological examination and ultrastructure observation showed the muscles were normal in the control groups. After 6 hours of ischemia, the skeletal muscles displayed injuries, and they were most severely injured after 12 hours of reperfusion. In the L-Arg group, the skeletal muscles were less injured, while in the L-NNA group, the injury was similar to that in the IR injury group. 　　Conclusions:　When the limbs of the rats sustain IR, NO in the blood decreases. Meanwhile, the muscles in the limbs are injured. When L-Arg is given, NO in the blood is restored and the muscles are protected. When L-NNA completely inhibits NO, no protection of the muscles is shown.