ABSTRACT
BACKGROUND: Studies have shown that nitric oxide(NO) can effectively improve blood supply and promote flap survival, but the specific mechanism is still unclear. OBJECTIVE: To explore the effects of L-arginine(L-Arg) on the survival of extended dorsal perforator skin flap in rats by activating L-Arg-NO pathway. METHODS: Animal models of extended dorsal perforator skin flap were successfully established in 81 male Sprague Dawley rats, which were then divided into a L-Arg group, a blank group and a L-NAME group. L-Arg(400 mg/kg per day) and nitro-amino-methyl-L-arginine(L-NAME; 40 mg/kg per day) were injected intraperitoneally in the L-Arg group and L-NAME group immediately and 1-7 days after operation, respectively, while the same volume of isotonic sodium chloride solution was injected intraperitoneally in the blank group at the same time points. Flap survival rate was measured. Angiography was performed to observe appearance and distribution of blood vessels at 7 days after operation. NO concentration of choke II zone was detected immediately, 1, 3, 5, and 7 days after operation. Tissue samples were harvested from the choke II zone for detecting density and caliber of new blood vessels using hematoxylin-eosin staining and the expression of vascular endothelial growth factor and matrix metalloproteinase was detected by western blot, respectively. The study protocol was approved by the Animal Ethics Committee of the 94 th Hospital of the PLA Joint Logistics Support Force(approval No. 2015 KYLL046). RESULTS AND CONCLUSION: The highest survival rate of flap appeared in the L-Arg group, (89.47±3.17)%, which was significantly higher than that in the other groups(F=49.908, P < 0.001). At 7 days after operation, the vascular structure in the choke II zone of the L-Arg group was relatively complete with clear trajectory. The vessels that had expanded to achieve true anastomosis extended along the longitudinal axis of the flap to the end of the flap. In the blank group and L-NAME group, the vascular structure and vascular trajectory in the choke II zone were disordered. Moreover, the vascular structure at the end of flap in L-NAME group disappeared. NO concentration in L-Arg group was increased after surgery, peaked at 3 days after operation, and then decreased gradually. Microvessel density and caliber in the L-Arg group were significantly higher than those in the other groups at 7 days after operation(P < 0.001). Western blot showed that the expression of vascular endothelial growth factor and matrix metalloproteinase-2 were significantly higher in the L-Arg group than the other groups at 3 after operation(P < 0.05), while at 7 days after operation, the expression of vascular endothelial growth factor in the L-Arg group was significantly higher than that in the other groups(P < 0.05), but the expression of matrix metalloproteinase-2 showed no significant difference among the three groups. To conclude, NO could promote microvascular growth and dilatation in the choke II zone of extended dorsal three-vascular perforator flaps in rats; L-Arg could increase the NO concentration in tissue by activating the L-Arg-NO pathway, which is beneficial to the survival of skin flap.
ABSTRACT
Objective: To observe the L-Arg (L-arginine) transport, the nitric oxide (NO) production, and NO synthase (NOS) activity in platelets, investigate the significance of the L-Arg-NO system in the pathogenesis of microvascular angina (MVA), and to study the reversing effects of intravenous L-Arg infusion on L-Arg transport. Methods: The 3H-L-Arg transport, NO production, and NOS activity in platelets were examined in 15 patients with MVA and 15 healthy controls. The 15 patients were given intravenous L-Arg infusion (20 g/d) after basic physical examination and were examined again 10 days later. Results: The L-Arg transport in platelets of MVA patients was obviously lower than that in the normal group; the maximum transport velocity (Vmax) decreased by 34. 4% compared with the normal group (P<0.01); and the Michaelis constant (Km) increased by 21.4% (P<0.05). The production of NO2- and the activity of NOS in platelets were decreased by 47.1% (P< 0.05) and 25.4% (P<0.05) compared with the normal group, respectively. Intravenous L-Arg infusion reversed the above changes in MVA patients; it increased the Vmax by 11.9% (P<0.01) and decreased Km by 18% (P<0.05); it also increased production of NO2- by 1.33 folds (P<0.05) and NOS activity by 1.2 folds (P<0.05). Especially, the attack of angina and patient ECG were greatly improved after intravenous L-Arg infusion. Conclusion: L-Arg-NO pathway is impaired in MVA patients, which might be responsible for the endothelium-dependent vascular relaxation in MVA patients. Intravenous L-Arg infusion may benefit the impaired function of L-Arg-NO transport in patients with MVA.