Platelet noradrenaline release in patients with familial hypercholesterolaemia

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Abstract
We have examined resting and thrombin (0.3 units ml-1) induced release of noradrenaline by washed platelets from 15 normal subjects and eight patients with heterozygous familial hypercholesterolaemia. Platelets from both normal and hypercholesterolaemic subjects showed irreversible aggregation with 0.3 units ml-1 thrombin. Extents of aggregation were 76.3% and 90.8% respectively, platelets from hypercholesterolaemic patients being significantly more sensitive (P < 0.002). Under resting conditions platelet noradrenaline release was 136% greater (PPPPP<0.01), no increases being observed with normal subjects. We suggest that platelet membranes may be more permeable in patients with familial hypercholesterolaemia leading to increased non-specific release of catecholamines. Platelets from patients with familial hypercholesterolaemia may also be more responsive to stimulation with respect to catecholamine release. The results obtained on calculation of total platelet noradrenaline levels may indicate that abnormalities of platelet dense granules occur in familial hypercholesterolaemia. In this context the relative proportions of free and conjugated catecholamine may be of relevance. The importance of lipoprotein-platelet interactions has been emphasized as regards the development of atherosclerosis. Platelet thrombus formation is also of undoubted importance in myocardial infarction. The platelet abnormalities described in this paper may contribute to the increased risk of premature vascular disease in patients with familial hypercholesterolaemia.