Effects of cationic polypeptides on thrombasthenic and afibrinogenemic blood platelets

Cationic polypeptides are known to cause the conversion of fibrinogen to fibrin gel and the immediate aggregation of blood platelets. In the present study, the effects of the cationic polypeptides, polybrene and polylysine, on normal, afibrinogenemic and thrombasthenic platelets were examined by nephelometry and electron microscopy. Normal and afibrinogenemic platelets aggregated rapidly and irreversibly after exposure to either agent. Thus, fibrinogen was not an essential factor for the interaction, though it may facilitate the rate of clumping produced by polybrene or polylysine. Thrombasthenic platelets did not aggregate rapidly or irreversibly in the presence of either agent. Shape change and slight degrees of clumping were induced by the cationic substances, a response essentially identical to the reaction of thrombasthenic platelets to collagen. The failure of cationic polypeptides to cause immediate aggregation of thrombasthenic platelets was not due to a failure of the agents to interact with the abnormal cells. Electron microscopy revealed that normal, afibrinogenemic and thrombasthenic platelets all adsorbed polybrene and polylysine, and transferred the agents to intracellular organelles.