Localization of calcium in red blood cells.
The distribution of calcium is demonstrated in human red blood cells (RBC) with a combined phosphate-pyroantimonate technique (PPA). Freshly collected blood and tissue biopsies were initially fixed in potassium phosphate-glutaraldehyde and the complexed calcium was subsequently visualized on Vibratome sections with potassium pyroantimonate. The majority of cells, both in isolated as well as "in situ" preparations, show a fine granular precipitate located at the inner leaflet of the plasma membrane. A minority of cells lack these membrane-associated deposits, exhibiting instead a random distribution of very fine precipitate in their cytoplasm. Capillary endothelial cells and pericytes are devoid of plasma membrane-bound precipitate. When irreversible crenation of RBC is induced by exposure to ionophore A 23187 and calcium, the sphero-echinocytes loose their membrane-bound precipitate, whereas the cells that retain their discocyte shape demonstrate the usual pattern of membrane-bound deposits. Contrarily, cells showing reversible shape changes induced by either A 23187-Ca2+ challenge, by adenosine triphosphate depletion during aging, or contact with lysolecithin, retain or regain the membrane-bound calcium. This cytochemical demonstrable calcium at the inner leaflet of the plasma membrane is probably bound to acidic phospholipids, since it is readily extractable with the nonionic detergent Triton X-100.
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood*; D002457:Cell Extracts / Q000032:analysis; D004910:Erythrocyte Membrane / Q000032:analysis / Q000648:ultrastructure; D004912:Erythrocytes / Q000032:analysis*; D004913:Erythrocytes, Abnormal / Q000032:analysis / Q000648:ultrastructure; D006801:Humans; D008051:Lipid Bilayers / Q000032:analysis; D009206:Myocardium / Q000032:analysis
D002457:Cell Extracts; D008051:Lipid Bilayers; D000001:Calcimycin; D002118:Calcium