Ischemia Pre-conditioning and the Effects of Nitric Oxide Synthase

Fifty male Sprague-Dawley rats were used in this study. The gracilis muscle flap with femoral vascular pedicle was dissected and used as a flap model. The ischemic preconditioning period consisted of three cycles of clamping the pedicle for 10 minutes followed by 10 minutes of reperfusion resulting in a total of 1 hour. In part I, the experimental group underwent the ischemic preconditioning for 1 hour. In the control group, the flaps were dissected without the clamping of the pedicle. Both groups were then subjected to 4 hours of global ischemia by continuous pedicle clamping, after which the flaps were sutured to their beds. Three days after the operation, the survival of the flaps was determined by gross and histological examinations. In part II, the experimental group underwent ischemic preconditioning, while the control group did not. The flaps from each group were harvested for iNOS gene expression using RT-PCR after 1 hour of perfusion and again after 4 hours of ischemia. The results indicated a significantly higher survival rate in the experimental group, with preconditioning than the non-preconditioned control group. iNOS gene expression was also significantly higher in the experimental groups than the control group at 1 hour after ischemic preconditioning. However, after 4 hours of global ischemia, iNOS expression in the control group was statistically higher than the experimental group. In conclusion, ischemic preconditioning can enhance flap tolerance to ischemic injury and improve flap survival rate. This study also provides evidence that the regulation of NOS may play an important role in the ischemic preconditioning phenomenon and thus the precise function of NOS in ischemia preconditioning warrants further investigation