ABSTRACT
<p><b>OBJECTIVE</b>To observe the effect of nitric oxide (NO) on the survival of a random pattern skin flap.</p><p><b>METHODS</b>Caudal based random skin flaps (9 cm x 3 cm) were raised on the back of Wistar rats. Six methods were used in the experiment to observe the effect of NO synthase inhibitor L-NAME and NO synthase substrate L-arginine on flaps: image analysis technology; light and electron microscopic studies; enzyme histochemistry of NOS in flaps; concentration of NO2-/NO3- in plasma and wet/dry ratio of the flap tissue.</p><p><b>RESULTS</b>Survival area of flap in the L-arginine-treated group significantly increased (67.06 +/- 5.65)% (p < 0.01) whereas the area in the L-NAME-treated group significantly decreased (35.17 +/- 1.87)% (p < 0.01) compared with the control group (53.25 +/- 3.24)% at seven days after the operation. General and microscopic observations showed that pathological changes in the L-arginine-treated group were fewer. Abundant capillaries and fewer inflammatory cells were noticed in the L-arginine-treated group. Transmission Electron Microscopy (TEM) studies find endothelial swelling, thrombosis-formation and endothelial loss of contact with the basement membrane in the L-NAME treated group. Before operation, the serum NO concentrations were not significantly different in three groups (p > 0.05). After operation, NO concentration of the control group began to increase and reached to the top at the third day. L-Arg kept serum NO concentration in a higher level than the control. Enzyme histochemistry of NOS in flaps: microvessel intima in dermis, hair follicles, sweat glands and inflammatory cells showed oxford blue, more positive in flaps of the L-Arg treated group than the control group at the third day after operation. The flaps of L-NAME-treated group demonstrated negative or weak positive. Wet/dry ratio: twenty-four hours after flap elevation wet/dry weight ratios increased significantly in all regions of the flap of the L-arginine-treated rats compared with saline-treated rats. The ratios of the flaps of L-NAME-treated rats were reduced compared with saline-treated rats.</p><p><b>CONCLUSION</b>NO could improve microcirculation of the flap and increase its survival rates. The mechanism might be that NO could accelerate flap vascularization and protect flaps from ischemia-reperfusion injury.</p>