REMNANT-LIKE LIPOPROTEINS STIMULATE WHOLE-BLOOD PLATELET-AGGREGATION IN-VITRO

We have developed a simple, rapid assay method to measure remnant- lik e lipoproteins by using an immunoaffinity gel mixture of anti apo B-10 0 and apoA-1 antobodies to Sepharose 4B. Characterization of the unbou nd lipoproteins has shown that they represent chylomicron and VLDL rem nant particles (RLP). Preincubation of whole blood with RLP resulted i n the enhanced activation of aggregation with ADP and collagen. Such e nhancement was not observed in the presence of lipoprotein deficient s erum or alubumin preparation. The extent of enhancement was 2.78 times by 7.5 mu M of ADP and 44 times by 0.5 mu g/ml of collagen in the pre sence of RLP-prepalation 1 (RLP-1), respectively. In the presence of R LP-2, the enhancement was 5.37 times by 7.5 mu M of ADP and 102 times by 0.5 mu g/ml of collagen, respectively. On the other hand RLP slight ly inhibited PRP aggregation by these agonists. Inhibitions were 19% b y 7.5 mu M of ADP and 18% by 1.0 mu g/of collagen in the presence of R LP-1, respectively. Incubation of whole blood with RLP did not result in the release of factors to stimulate platelets or ADP- or collagen-i nduced platelet aggregation in vitro. The extents of enhanced aggregat ion in whole blood or inhibition in PRP were not correlated with RLP-c holesterol nor RLP-protein concentrations of RLP preparations used. Th ese results may indicate that RLP not only interact with platelets but with erythrocytes or leukocytes. Our findings support the hypothesis that the postprandial increase in remnant lipoproteins is an atheroscl erotic risk factor and may be a part of the reasons of thrombotic comp lications by stimulating platelets inpatients with remnant hyperlipopr oteinemia.