Effect of Ferriprotoporphyrin IX and Non-heme Iron on the Ca2+ Pump of Intact Human Red Cells

Effect of Ferriprotoporphyrin IX and Non-heme Iron on the Ca2+ Pump of Intact Human Red Cells Previous studies have shown that ferriprotoporphyrin IX (FP) and non-heme iron have a marked inhibitory effect on the Ca2+-Mg2+-ATPase activity of isolated red cell membranes, the biochemical counterpart of the plasma membrane Ca2+ pump (PMCA). High levels of membrane-bound FP and non-heme iron have been found in abnormal red cells such as sickle cells and malaria-infected red cells, associated with a reduced life span. It was important to establish whether sublytic concentrations of FP and non-heme iron would also inhibit the PMCA in normal red cells, to assess the possible role of these agents in the altered Ca2+ homeostasis of abnormal cells. Active Ca2+ extrusion by the plasma membrane Ca2+ pump was measured in intact red cells that had been briefly preloaded with Ca2+ by means of the ionophore A23187. The FP and nonheme iron concentrations used in this study were within the range of those applied to the isolated red cell membrane preparations. The results showed that FP caused a marginal inhibition (∼20%) of pump-mediated Ca2+ extrusion and that non-heme iron induced a slight stimulation of the Ca2+ efflux (11–20%), in contrast to the marked inhibitory effects on the Ca2+-Mg2+-ATPase of isolated membranes. Thus, FP and non-heme iron are unlikely to play a significant role in the altered Ca2+ homeostasis of abnormal red cells. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Effect of Ferriprotoporphyrin IX and Non-heme Iron on the Ca2+ Pump of Intact Human Red Cells

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Copyright © 2000 by Springer-Verlag New York Inc.
Life Sciences; Biochemistry, general; Human Physiology
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