Platelet noradrenaline and adrenaline efflux in hypercholesterolaemia: studies in platelet-rich plasma

Collagen-induced (5-80 microg/ml) efflux of free noradrenaline (NA) and adrenaline (Ad) from platelets in platelet-rich plasma was compared in normal human subjects and heterozygous familial hypercholesterolaemic (FH) patients. Stimulated release of NA and Ad to the plasma (platelet-poor; PPP) increased in a dose-dependent fashion in both normal and FH groups. Under resting conditions (0 microg/ml collagen) PPP NA concentrations were increased in hypercholesterolaemics by 38% (non-significant). The absolute amounts of NA released on stimulation with 5 microg/ml and 10 microg/ml collagen (i.e. the differences between resting and stimulated release) were reduced in hypercholesterolaemics by 45% (p<0.01) and 38% (p<0.02), respectively. Collagen EC50 values for NA and Ad release were increased in hypercholesterolaemics by 118% (p<0.001) and 141% (p<0.05). Combining the data for the normal and FH groups revealed that the collagen EC50 values for NA release correlated positively with plasma total cholesterol (p<0.02) and low-density lipoprotein (p<0.02). These data provide additional evidence for catecholaminergic abnormalities in hypercholesterolaemia.