BACKGROUND: Thrombotic diseases always accompany with blood rheological abnormality. Whether allicin has effects on hemorheological indexes and physiological characteristics of erythrocyte needs to further study.OBJECTIVE: To investigate the effect of allicin on hemorheological indexes and physiological characteristics of erythrocyte in rats with acute blood hyperviscosity.DESIGN: Purely randomly controlled animal study.SETTING: College of Food Science and Nutritional Engineering, China Agricultural University.MATERIALS: A total of 50 Wistar rats of half gender, weighing (200±20) g and aged from 3 to 4 month were provided by Beijing Haidian Tongli Experimental Animal Cultivation Center. Allicin solution was provided by Shanghai Hefeng Pharrnaceutical Co., Ltd. (cencentration: 15 g/L; batch number: 20051001). The main equipments were detailed as follows: NXE-1 cone-plate viscometer (Chengdu Device Factory), DXC-300 nuclear pore membrane erythrocyte deformation radiometer (Device Factory Affiliated to Shanghai Medical University), 650-60 fluorescence polarization (Hitachi Company, Japan) and trace high speed centrifugation (Huaxing Aviation Aircraft Company, Aerospace Faulty).METHODS: The experiment was carried out in the Laboratory of College of Food Science and Nutritional Engineering,China Agricultural University from February to April 2006. All rats were randomly divided into 5 groups, including control group, model group, low-dosage allicin group, moderate-dosage allicin group and high-dosage allicin group, with 10 in each group. Except control group, rats in other 4 groups were perfused with 5 mL tap-water every day fcr 7 successive days. On the seventh day, rats were subcutaneously injected with 0.1% 0.8 mL/kg adnephrin; 2 hours later, rats were dripped in iced water for 5 minutes; 4 hours later, the rats were injected again to establish models of acute blood hyperviscosity. Two days later, all rats in the control group and model group were intraperitoneally injected with saline hematocrit and erythrocyte aggregation index were measured with viscosity determination method; erythrocyte filtration index was measured with nuclear pore membrane flow rate method; erythrocyte membrane fluidity (erythrocyte fluorescence polarization) was measured with fluorescence polarization technique; erythrocyte osmotic fragility test (concentration of NaCl solution from the beginning hemolysis to complete hemolysis) was performed to compare various indexes among different groups.MATN OUTCOME MEASURES: ① Effect of allicin on erythrocyte aggregation (whole blood viscosity,plasma viscosity,hematocrit and erythrocyte aggregation index);② effect of allicin on erythrocyte deformability index (filtration index);③ effect of allicin on erythrocyte osmotic fragility (concentration of NaCl solution from the beginning hemolysis to complete hemolysis);④ effect of allicin on erythrocyte membrane fluidity (erythrocyte membrane fluorescence polarization).RESULTS: Among 50 rats, 8 rats did not have enough blood collection or died; therefore, other 42 rats were involved in the final analysis. ① Effect of allicin on erythrocyte aggregation: As compared with that in the model group, whole blood viscosity was decreased 14.43%, 9.71% and 4.15% in high-dosage, moderate-dosage and low-dosage groups,respectively (P ＜ 0.05-0.01); meanwhile, whole blood viscosity of low shear rate was decreased 15.89%, 14.27% and 6.86%, respectively (P ＜ 0.01), and plasma viscosity was decreased 11.33% (P ＜ 0.05), 9.78% (P ＜ 0.05) and 3.49% (P＞ 0.05), respectively. And the effects mentioned above were shown a dose-effect relationship. Allicin in a high dosage could obviously decrease hematocrit (P ＜ 0.05) and the decreasing degree was 6.47%.② Effect of allicin on erythrocyte deformability index: Filtration index was higher in the model group than that in the control group (0.228±0.025, 0.175±0.043, P ＜ 0.05); however, filtration index was lower in the high-dosage allicin group (0.176±0.034) than that in the model group (P ＜ 0.05). ③ Effect of allicin on erythrocyte osmotic fragility: Concentration of NaCl was higher in the model group than that in the control group at the beginning of hemolysis and at the phase of complete hemolysis. Moreover, allicin in various dosages could improve the increase of erythrocyte osmotic fragility, but there were no significant differences among different dosage groups. ④ Effect of allicin on erythrocyte membrane fluidity: Erythrocyte membrane fluorescence polarization was increased in the model group, and this suggested that membrane fluidity was decreased. Allicin could improve the decrease of erythrocyte membrane fluidity, but there were no significant differences among various dosage groups.CONCLUSION: Allicin can raise erythrocyte deformability, decrease blood viscosity, improve blood fluidity, prevent and cure blood stasis syndrome.