RESUMO
OBJECTIVE: To observe the effects of low-level laser irradiation on mesenteric microcirculation of rats in vivo in the early stage of endotoxemia (ETM). METHODS: The experimental model of ETM was reproduced by injection of lipopolysaccharide (LPS). Sixty healthy male Sprague-Dawley (SD) rats were divided into three groups used random number table: control group, LPS group and low-level laser irradiation group, each group included 20 rats which were subdivided into four temporal subgroups (1, 2, 4, 6 hours, respectively). In low-level laser irradiation group, the rats were irradiated by type SLT semiconductor laser (650 nm, 5 mW) on unilateral femoral artery and vein, and blood vessel of the ear concurrently for 30 minutes. The interference course was vertical irradiation taken at 30 minutes after the injection of LPS. At 1, 2, 4, 6 hours after the injection of LPS, changes in mesenteric microcirculation and microcirculatory blood flow were recorded with the laser Doppler flowmeter, the velocity of red blood cells in venules was observed, and the number of open capillaries and adherent leukocytes were recorded. RESULTS: The blood flow velocity (mm/s) of the mesenteric microcirculation in LPS group was accelerated at 1 hour and 2 hours after LPS injection (1 hour: 0.190+/-0.007 vs. 0.174+/-0.009, 2 hours: 0.200+/-0.010 vs. 0.172+/-0.015, both P<0.05, respectively), but decelerated at 6 hours (0.116+/-0.015 vs. 0.164+/-0.011, P<0.05). The blood flow volume in the mesenteric vessels and the number of open capillaries did not show any significant change at that time. Significant increase in number of adherent leukocytes was observed at 2, 4, 6 hours after injury (2 hours: 2.60+/-1.14 vs. 0.40+/-0.55, 4 hours: 5.40+/-0.89 vs. 0.40+/-0.55, 6 hours : 5.40+/-1.52 vs. 0.60+/-0.90, all P<0.05, respectively). The state of blood flow in the microcirculation became abnormal. After irradiated with laser in low dose, the blood flow velocity was smooth and stable (mm/s, 1 hour: 0.174+/-0.011, 2 hours: 0.180+/-0.023, 4 hours: 0.168+/-0.013, 6 hours: 0.162+/-0.023), and the number of adherent leukocytes was reduced significantly at 4 hours and 6 hours than that in LPS group (4 hours: 2.00+/-0.71 vs. 5.40+/-0.89, 6 hours: 2.60+/-1.52 vs. 5.40+/-1.52, both P<0.05) and the microcirculatory flow state was improved obviously. CONCLUSION: Low-level laser irradiation may ameliorate the local mesenteric microcirculation, alleviate the microcirculatory disorder in early stage of ETM.
