Summary
The kinetics, in vivo distribution and sites of sequestration of autologous In-111-labelled platelets and
other platelet function parameters were studied in ten patients with type IIa or IIb
familial hypercholesterolaemia and thrombotic complications of atherosclerosis. The
in vitro platelet aggregation response to ADP (P = 0.50) and collagen (P = 0.46); binding
of fibrinogen to platelets (P = 0.61); and plasma beta-thromboglobulin levels (P =
0.42) of the patients and normal reference subjects did not differ significantly.
The in vivo distribution of In-111-labelled platelets at equilibrium was within normal limits,
and at the end of platelet life-span the sequestration pattern of labelled platelets
in the reticuloendothelial system was also normal (spleen P = 0.31; liver P = 0.54).
There was minimal evidence of in vivo platelet activation: only mean platelet lifespan (MPLS), 195±57 hours (difference
between mean MPLS of patients and controls was 25 hours, with a 95% confidence interval
from 23 to 31 hours; P = 0.02); mean platelet platelet turnover, 2298±824 platelets/μl/hour
(P = 0.005); plasma platelet factor 4 (P = 0.02); and the mean circulating platelet
aggregate ratio, 0.8±0.1 (P = 0.02); differed significantly from normal. These results
suggest that abnormalities of platelet function and kinetics observed in type II hyperlipoproteinaemia
cannot be ascribed wholly to the hyperlipidaemia, but may be induced by the associated
atherosclerosis.
Keywords
Hypercholesterolaemia - In-111-labelled platelets - Platelet function - Platelet kinetics
- Platelet lifespan
