Platelet function in a case with abetalipoproteinemia.

Platelet aggregation, [14C]serotonin release and platelet malondialdehyde production were determined in a patient with abetalipoproteinemia (ABL) and found to be normal. The patient demonstrated complete absence of apolipoprotein (apo) B and decreased apo A-I concentration in plasma. The high density lipoprotein (HDL) composition of plasma was abnormal, with an increased cholesterol/protein ratio, increased apo E levels and reduced apo C concentration. The patient's platelets, like platelets derived from a normolipidemic control, possessed receptors capable of binding lipoproteins. On incubating washed platelets derived from a control subject with HDL obtained from the ABL patient, an enhancement in platelet function was observed. A similar concentration of HDL derived from the control had the opposite effect, a depression of platelet function. Lipoprotein-deficient plasma (LPDP) derived from the patient, on the other hand, decreased platelet aggregation and [14C]serotonin release in comparison to the LPDP obtained from the control. The normal platelet function observed in the patient appears to be the result of the platelet-enhancing effect of an abnormal HDL, thus compensating for the absence of low and very low density lipoproteins from the patient's plasma which, when present, stimulate platelet function.