Myosin content and distribution in human neonatal erythrocytes are different from adult erythrocytes.
Neonatal erythrocytes (N-RBC) are different from adult erythrocytes (A-RBC). N-RBC are larger, less deformable, and undergo enhanced spontaneous and drug-induced endocytosis. The reticulocyte population of N-RBC is also different, consisting primarily of the youngest (R1) reticulocytes that are motile and capable of receptor-mediated endocytosis. Processes such as motility could require a contractile system. Myosin, a contractile protein, was identified in both A-RBC and N-RBC. We proposed to compare myosin content and distribution in A-RBC and N-RBC by immunofluorescence and enzyme-linked immunosorbent assay (ELISA) using a monospecific polyclonal rabbit antimyosin. There was bright immunofluorescence on 44% of N-RBC with some heterogeneity contrasting with a barely detectable fluorescence on A-RBC. ELISA measurements showed that A-RBC had 4,315 myosin copies/RBC, whereas N-RBC had 10,855 copies/RBC (or 2.5 times as much). ELISA measurements of white ghosts showed that A-ghosts contained 1,250 copies of myosin/RBC (29% of total) whereas N-ghosts contained 3.4 times as much at 4,320 copies/RBC (39% of total). Therefore, N-RBC not only have more myosin, but the amount that is membrane-associated is disproportionately increased. It is proposed that such differences in amount and distribution of myosin could account for some of the unusual properties of neonatal RBC indicated.
Colin
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Division of Hematology, Stanford University School of Medicine, CA 94305-5112.
Schrier
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D000328:Adult; D000367:Age Factors; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007231:Infant, Newborn / Q000097:blood; D009218:Myosins / Q000097:blood*; D013049:Spectrin / Q000378:metabolism
D013049:Spectrin; D009218:Myosins