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Sickle red cell calcium metabolism: Studies on Ca 2+ ‐Mg 2+ ATPase and ca‐binding properties of sickle red cell membranes
Author(s) -
Litosch Irene,
Lee Kwang Soo
Publication year - 1980
Publication title -
american journal of hematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.456
H-Index - 105
eISSN - 1096-8652
pISSN - 0361-8609
DOI - 10.1002/ajh.2830080406
Subject(s) - membrane , calcium , red cell , chemistry , calmodulin , atpase , cell , biophysics , red blood cell , population , biochemistry , calcium pump , cell membrane , hemolysis , biology , medicine , enzyme , immunology , environmental health , organic chemistry
Sickle (Hb SS) red cells, preloaded with 45 Ca by reversal of hemolysis, exhibit an incomplete 45 Ca extrusion, retaining approximately four times more 45 Ca than normal cells. Studies indicated that neither the reduction in Hb SS cell Ca 2+ ‐Mg 2+ ATPase activity (84% of normal) nor the activation of Ca 2+ ‐Mg 2+ ATPase by calmodulin was sufficiently different from normal cells to attribute a major role to the calcium pump in 45 Ca retention. These results suggested that 45 Ca retention may reflect an alteration in the calcium‐binding properties of Hb SS cell membranes. Low‐affinity calcium‐ binding (freely dissociable) was similar in normal and Hb SS cell membranes. However, the total calcium bound with high‐affinity (tightly bound) was four‐to‐five times greater in Hb SS cell membranes than in normal membranes. These results are compatible with the hypothesis that Hb SS cell 45 Ca retention reflects an exchange of a fraction of the total 45 Ca with a tightly bound calcium pool, larger in Hb SS cell membranes than in normal membranes. A comparable degree of red cell 45 Ca retention, which did not correlate with the reticulocyte population, was observed in other chronic anemic states. These findings suggest that the increased high‐affinity calcium binding by the membrane may be a consequence of cellular changes induced by the anemic condition.