Human erythrocytes shed exocytic vesicles in vivo

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Abstract
Studies were designed to demonstrate whether red cells (RBCs) lose membrane segments in vivo. Plasma separated from fresh blood collected in citrate‐phosphate‐dextrose‐adenine‐one was passed through 0.8 mu nitrocellulose filters to remove residual RBCs and formed elements. Exocytic vesicles were separated by centrifugation at 70,000 × g. Transmission electron microscopy showed vesicles 50 to 200 nm in diameter which contained hemoglobin. Sodium dodecyl sulfate‐ polyacrylamide gel electrophoresis of vesicle membranes showed that spectrin bands 1 and 2 and ankyrin band 2.1 were absent. These observations are the initial demonstration that RBCs shed exocytic vesicles in the normal circulation.