A high concentration of collagen induces Gαq-independent aggregation.

Gαq-deficient (Gαq^−/−) and wild-type (WT) platelets were stimulated with a high level (50 μg/mL) of collagen. Gαq-deficient platelets aggregated in response to a high level of collagen, and the extent of aggregation was undiminished in comparison to wild-type platelets (A). Gαq-deficient platelets secrete ATP (B) and produce TxA2 (C) to a level similar to that of the wild-type platelets. Data were obtained from 2 tests. Bars represent means ± SEM.