Native and oxidized low density lipoproteins enhance platelet aggregation in whole blood.

The effects of native and oxidized low density lipoproteins on platelet aggregability remain controversial despite numerous studies. In the current investigation, effects of native, minimally and extensively copper-modified low-density lipoproteins on aggregation responses to ADP and collagen in platelet-rich plasma, washed platelets, and whole blood were studied. Preincubation with native and oxidized low-density lipoproteins (1.5-23.2 malondialdehyde equivalents [MDAeq]/mg low density lipoprotein) did not modify aggregability in platelet-rich plasma or washed platelets but increased aggregation markedly in whole blood (40-58%, p<0.01). In whole blood, the increase in response to ADP was not affected by the degree of low-density lipoprotein oxidation. This comprehensive investigation of low density lipoprotein effects on platelet aggregation therefore has demonstrated that low density lipoproteins indirectly increase platelet aggregability in whole blood, but not in platelet-rich plasma and washed platelets, presumably via an interaction between platelets and other formed elements of blood.