The effect of spicules obtained from sickle red cells on clotting activity.

Spicules from sickle red cells were examined for their effects on the clotting activity of blood. The spicules were obtained from the sickle red cells after deoxygenation and oxygenation and were tested for clotting activity with Russell's viper venom assay. A marked increase in clotting activity was observed when spicules were added to the system. The increase was distinctly greater than that observed after the addition of sickle red cells while normal red cells had little effect. Vesicles prepared from sickle or normal red cells by incubation with the ionophore A-23187+Ca2+ also markedly increased clotting activity. The effect of spicules or vesicles on the clotting system may be related to reorganization of phospholipid in the spectrin-poor membrane of the spicules or vesicles. Because of these effects, the spicules from the sickle red cells may contribute to the hypercoagulable state in these patients and possibly to their vaso-occlusive crises since free spicules are present in their plasma. Vesicles from red cells from other types of anaemia with hypercoagulability may have a similar effect on coagulation.