Extracellular calcium is required for the maintenance of plasma membrane integrity in nucleated cells |
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Authors: | Orlov Sergei N Aksentsev Sergei L Kotelevtsev Sergei V |
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Institution: | Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia. sergei.n.orlov@umontreal.ca |
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Abstract: | In contrast to rat and human erythrocytes, nucleated erythrocytes from two fish species (Cyprinus carpio and Salmo trutta) underwent almost complete haemolysis in 20 min of EDTA addition. Using Ca2+/Mg2+ EGTA-citrate buffer, we observed that half-maximal haemolysis of fish erythrocytes occurs at Ca2+]o approximately 10 microM independently of extracellular Mg2+ concentration. Attenuation of Ca2+]o with EGTA also decreased stability of the plasma membrane of vascular smooth muscle cells (VSMC) and HeLa cells, indicated by a three- to five-fold elevation of lactate dehydrogenase release and passive permeability of plasma membrane for Na+. In VSMC, EGTA lowered Ca2+]i by approximately 20%. This effect was absent in VSMC-loaded with the intracellular Ca2+ chelator BAPTA. In contrast to EGTA, BAPTA did not affect haemoglobin release from fish erythrocytes and passive permeability for Na+ in VSMC. Viewed collectively, our data show that in nucleated cells, extracellular Ca2+ plays a crucial role in the maintenance of plasma membrane integrity. |
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