title: Extracellular calcium is required for the maintenance of plasma membrane integrity in nucleated cells.
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.
authors.affiliation: Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia. sergei.n.orlov@umontreal.ca
authors.forename: Sergei N
authors.initials: SN
authors.lastname: Orlov
authors.forename: Sergei L
authors.initials: SL
authors.lastname: Aksentsev
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Kotelevtsev
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005399:Fishes; D006367:HeLa Cells; D006454:Hemoglobins / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism
chemical_list: D006454:Hemoglobins; D004533:Egtazic Acid; D012964:Sodium; D007770:L-Lactate Dehydrogenase; D008274:Magnesium; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium