title: Lipoproteins inhibit platelet aggregation and arachidonic acid metabolism in experimental hypercholesterolaemia.
abstract: 1. Human plasma contains unidentified components that inhibit arachidonic acid (AA) metabolism. In the present study, we investigated whether plasma from rabbits fed a normal or high-cholesterol diet for 16 weeks also inhibits AA metabolism. Specifically, we studied the effects of plasma on platelet aggregation and on the production of AA metabolites, tri-hydroxyeicosatrienoic acid, 12-hydroxyeicosatetraenoic acid and thromboxane B(2). 2. Haematological and lipid profiles were altered by a high-cholesterol diet. Platelets from hypercholesterolaemic rabbits showed enhanced aggregatory sensitivity to AA and platelet-activating factor. However, plasma from hypercholesterolaemic and control rabbits, when added to the incubation mixture, significantly inhibited platelet aggregation and eicosanoid production. 3. High- and low-density lipoprotein (HDL and LDL, respectively) concentrations increased several-fold in plasma with cholesterol feeding. When added directly to the incubation mixture, both HDL and LDL inhibited platelet aggregation, as well as AA metabolism. 4. Haptoglobin, albumin and Cohn's fraction IV, but not globulins, exhibited antiplatelet and anti-AA metabolism activities. Their concentrations in plasma were not affected by cholesterol feeding. 5. We conclude that LDL and HDL account for at least some of the inhibition of AA metabolism produced by plasma.
authors.affiliation: Canadian Blood Services, Department of Laboratory Medicine and St Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Rukhsana
authors.initials: R
authors.lastname: Aslam
authors.forename: Sheikh A
authors.initials: SA
authors.lastname: Saeed
authors.forename: Sagheer
authors.initials: S
authors.lastname: Ahmed
authors.forename: John D
authors.initials: JD
authors.lastname: Connor
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D002784:Cholesterol; D004041:Dietary Fats / Q000009:adverse effects* / Q000097:blood; D006937:Hypercholesterolemia / Q000378:metabolism*; D008074:Lipoproteins / Q000494:pharmacology*; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects*; D011460:Prostaglandins F / Q000097:blood; D011817:Rabbits; D013929:Thromboxane B2 / Q000097:blood; D013997:Time Factors
chemical_list: D004041:Dietary Fats; D008074:Lipoproteins; D011460:Prostaglandins F; D016718:Arachidonic Acid; D013929:Thromboxane B2; D002784:Cholesterol; C100006:prostaglandin F1