ADP-INDUCED 2ND WAVE AGGREGATION IN PLATELET RICH PLASMA FROM HYPERCHOLESTEROLEMIC RABBITS

Platelet aggregation, ATP secretion and thromboxane formation were measured in platelet-rich plasma (PRP) of rabbits fed a cholesterol-rich (1%) diet for 3 months. Addition of ADP (0.6 - 2-mu-M) resulted in a clear biphasic aggregation in 7/8 cholesterol-fed rabbits. This was not seen in any of the 9 control animals kept on a standard diet for the same period of time (P < 0.01). The secondary ADP-induced aggregation was irreversible and was accompanied by enhanced ATP secretion and significant thromboxane generation. There was no ADP-induced thromboxane formation and only a minor ATP secretion at the highest ADP concentration studied (20-mu-M) in control rabbits. These data confirm platelet hyperreactivity in hypercholesterolemia and demonstrate for the first time the occurence of an ADP-induced second wave aggregation and granule secretion in citrated PRP of rabbits which may be triggered by thromboxane generation.