Abstract: Abstact   Objective   To investigate the effect of High Density Lipoprotein on expression of CD62P and CD63 on thrombin-activated platelet in vitro. Methods   Equivalent volume of washed platelet prepared by hand was preincubated with HDL(1mg/ml) in 37℃ water for 15 minutes ，then stimulated with different concentrations of thrombin(0.5U/ml,1U/ml,10U/ml) for 10 minutes in water of 37℃.Meanwhile another three groups of washed platelet was incubated with thrombin(0.5U/ml,1U/ml,10U/ml) for 10minutes,respectively.The CD62P and CD63 from each sample were analyzed by flow cytometry(FCM). Results   The CD62P positive rate of HDL-preincubated groups were significantly lower than the groups of different concentrations of thrombin(0.5U/ml,1U/ml,10U/ml) in the absence of HDL, 11.55%±1.34% vs 18.14%±1.50%,17.19%±0.17% vs 26.24%±0.77%,19.79%±0.32% vs 80.38%±5.66%;P value <0.001.Meanwhile, The CD63 positive rate of HDL-preincubated groups were also significantly lower the thrombin-treated (0.5U/ml,1U/ml,10U/ml) groups without HDL,namely,8.09%±0.48% vs 2.92%±0.22%(P<0.001),14.15%±1.39% vs 4.20%±0.98%(P<0.001),24.48%±1.71% vs 5.12%±0.09%(P<0.001). Conclusion   HDL inhibits expression of alpha-granulemembrane protein (CD62P) and lysosome intact membrane protein(CD63) on thrombin-stimulated platelet in vitro.

Key words: poproteins, HDL, P-selectin, thrombin, flow cytometry, lysosomal-associated membrane protein 1, antigens, CD36