1. Repeated plasma exchange was carried out on three young patients with severe familial hypercholesterolaemia. There was a 3 week interval between each exchange. After a single exchange, plasma cholesterol, apolipoprotein B and low density lipoprotein-cholesterol levels decreased markedly, but pre-exchange levels were not achieved within 2 weeks. High density lipoprotein-cholesterol and apolipoprotein A-I levels also fell but returned to the original concentration after only 5 days. 2. Platelet aggregation and [14C]serotonin release were increased in all three patients and dropped by 20% and 13% respectively after a single plasma exchange. Platelet function in vitro returned to pre-exchange levels with similar kinetics to that observed with the low density lipoprotein concentration. On removal of 100 g of plasma cholesterol, after repeated exchanges, low density lipoprotein concentration and platelet function were significantly decreased in comparison with values before initiation of plasma exchange. In addition there was a marked regression of xanthoma in all three patients. 3. Since this procedure is instrumental in achieving a negative cholesterol balance as well as inhibiting hypersensitive platelets, it may well result in a downgrading of the atherosclerotic risk.

Dibutyryl cyclic AMP, forskolin, dipyridamole and butyl imidazole inhibited platelet aggregation (induced by ADP or collagen) in washed platelets more than in platelet‐rich plasma preparations. Aspirin, indomethacin and epoprostenol (prostacyclin, PGI2) showed no preferential inhibition of these platelet preparations. When platelet‐ rich plasma from either normal or familial hypercholesterolaemic (FH) subjects was used, aspirin, indomethacin and dipyridamole (but not forskolin) inhibited platelet aggregation in normal subjects more than in FH patients. When low doses of aspirin (75 mg daily for 7 days) or dipyridamole (250 mg, single dose) were administered in vivo, platelet aggregation was inhibited more in the normal subjects in comparison to the patient group.

Ten healthy women in their tenth decade of life were compared with ten healthy women in their fourth decade of life regarding the response of plasma lipoproteins and platelet aggregation to one meal rich in saturated fats. In the elderly group, plasma cholesterol decreased in the postprandial state three hours after the meal in comparison to no significant changes in the younger group. This resulted from reduction in plasma lipoprotein cholesterol levels, except for the high-density lipoprotein (HDL) cholesterol, which was enhanced. A similar pattern was found for plasma lipoprotein levels. The increase in plasma triglyceride concentration in the elderly women was less than in the younger women, as fewer changes in their plasma triglyceride-rich lipoproteins (chylomicrons and very-low-density lipoprotein) were observed. Platelet aggregation in response to collagen was reduced in the elderly women, whereas in the younger group, increased platelet aggregation in the postprandial state was found. Our study thus demonstrates a clear advantage of the elderly women in comparison to the younger ones in reducing atherosclerosis and thrombotic risks. The elderly group responded to the saturated fat-rich meal by minimal plasma triglyceride elevation, an increase in HDL cholesterol concentration, and reduced platelet aggregation.