Platelet function in C6-deficient rabbits. Aggregation and secretion induced by collagen and zymosan.

Platelet aggregation and the selective release of 5-hydroxytryptamine (5HT) and adenine nucleotides were measured in platelet-rich plasma (PRP) and washed platelet suspensions from control and C6-deficient rabbits. Aggregation and release induced by collagen were similar in both groups of animals. Aggregation responses to zymosan in control PRP samples were biphasic, and only the second phase was associated with release. In C6-deficient PRP samples, zymosan-induced aggregation lacked the second phase and there was no release of 5HT or adenine nucleotides. Zymosan induced no aggregation in washed platelet suspensions unless cell-free plasma was also added. C6-deficient plasma supported only primary aggregation, but the addition of control plasma resulted in biphasic aggregation and release. Zymosan which had been pre-activated in control or C6-deficient cell-free plasma induced primary aggregation in washed platelet suspensions. To obtain secondary aggregation and release, the addition of control plasma to the platelet suspension was necessary.