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

Collagen-induced (5-80 mug/ml) efflux of free noradrenaline (NA) and adrena line (Ad) from platelets in platelet-rich plasma was compared in normal hum an subjects and heterozygous familial hypercholesterolaemic (FH) patients. Stimulated release of NA and Ad to the plasma (platelet-poor; PPP) increase d in a dose-dependent fashion in both normal and FH groups. Under resting c onditions (0 mug/ml collagen) PPP NA concentrations were increased in hyper cholesterolaemics by 38% (non-significant). The absolute amounts of NA rele ased on stimulation with 5 mug/ml and 10 mug/ml collagen (i.e. the differen ces between resting and stimulated release) were reduced in hypercholestero laemics by 45% (p<0.01) and 38% (p<0.02), respectively. Collagen EC50 value s 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 abnormaliti es in hypercholesterolaemia.