Effect of oxidized low density lipoproteins on the structure of platelet membrane. Use of electron paramagnetic resonance]

The effect of low-density lipoproteins on the structure of platelet plasma membrane was studied by electron paramagnetic resonance spectroscopy. Low-density lipoproteins were incubated with platelet rich plasma at a volume ratio 1:1. Plasma incubated with buffer served as a control. After incubation, the fluidity of platelet plasma membrane was determined by electron spin resonance probes 5-doxylstearate and 16-doxylstearate, which were immobilized in membranes of cells subjected to triple precipitation. Significant differences in the order parameter S, which characterizes the spectrum of the 5-doxylstearate probe, for samples incubated with the buffer and oxidized low-density lipoproteins were found. The dependence of the parameter on incubation time and the extend of oxidation of low-density lipoproteins were obtained. No significant differences in rotational correlation time of 16-doxylstearate between platelets incubated with and without oxidized low-density lipoproteins was observed within the limits of experimental error; however, the changes in the half-width of the low-field component may be considered reliable. The interaction of oxidized low-density lipoproteins with platelets leads to an increase in plasma membrane fluidity, thereby mediating the activating action on platelets.