Does low concentration of LDL enhance human blood platelet reactivity in vitro?
In vitro exposure to low concentrations of LDL induces primary activation of human platelets and enhances their sensitivity to thrombin.
The isolated low density lipoprotein (LDL) has been shown to cause shape change, granule centralization and incomplete degranulation of human blood platelets at concentrations of 50 to 300 μg protein/ml in vitro. About half the number of platelets were discoid at the LDL concentration of 50 μg/ml. If the platelets were pretreated with LDL at a concentration of 100 μg/ml, aggregation could be induced by thrombin (0.015 U/ml) lightly. These results suggested that the LDL-incubated platelets showed a primary activation. These LDL-pretreated platelets showed enhanced sensitivity to thrombin by aggregating at a very low dosage (0.015 U/ml). The primary activation of platelets induced by LDL seemed independent of extracellular calcium when LDL concentrations were higher than 200 μg/ml.
Zhao et al. (1993) studied this question.