Circulating proplatelets: isolation and quantitation in healthy rats and in rats with induced acute blood loss.

A technique to isolate megakaryocyte proplatelet processes from blood of rats' hearts, using colloidal silica coated with polyvinylpyrrolidone density gradient, was developed. The proplatelet concentration in blood from right ventricles was significantly higher (P less than 0.001) than that in blood from left ventricles in healthy rats, as well as in rats with induced acute blood loss. The proplatelet concentration of blood from the heart, 24 hours after acute blood loss was induced was significantly (P less than 0.001) increased, indicating that platelet production was accelerated. The demonstration of proplatelets entering the pulmonary circulation indicates platelet release via proplatelet formation. Seemingly, proplatelets are fragmented in the lungs at predesignated locations along the proplatelet process.