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Monovalent cation (MC) current in cardiac and smooth muscle cells: regulation by intracellular Mg 2+ and inhibition by polycations
Author(s) -
Zakharov Sergey I,
Smani Tarik,
Leno Endri,
Macianskiene Regina,
Mubagwa Kanigula,
Bolotina Victoria M
Publication year - 2003
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0705074
Subject(s) - extracellular , intracellular , spermine , biophysics , chemistry , bapta , depolarization , divalent , myocyte , vascular smooth muscle , microbiology and biotechnology , biochemistry , endocrinology , biology , smooth muscle , organic chemistry , enzyme
Previously we have described a monovalent cation (MC) current that could be unmasked by the removal of extracellular divalent cations in vascular smooth muscle cells (SMC) and cardiac myocytes, but specific and potent inhibitors of MC current have not been found, and the mechanism of its intracellular regulation remains obscure. Here we show that small MC current is present in intact cells and could be dramatically up‐regulated during cell dialysis. MC current in dialyzed cells strongly resembled monovalent cation current attributed to Ca 2+ release‐activated Ca 2+ ‐selective (CRAC) channels, but its activation did not require depletion of Ca 2+ stores, and was observed when the cells were dialyzed with, or without BAPTA. Intracellular free Mg 2+ inhibits MC current with K d =250 μ M . Extracellular (but not intracellular) spermine effectively blocked MC current with K d =3–10 μ M , while store‐operated cations (SOC) channels and capacitative Ca 2+ influx were not affected. Spermine effectively inhibited MC current‐induced SMC depolarization, and prevented Ca 2+ paradox‐induced vascular contracture. Both, MC and SOC currents were inhibited by 2‐aminoethoxydiphenyl borate (2‐APB). It is concluded that MC current could be regulated by intracellular Mg 2+ , and low concentrations of extracellular spermine could be used to discriminate it from SOC current, and to assess its role in cellular function.British Journal of Pharmacology (2003) 138 , 234–244. doi: 10.1038/sj.bjp.0705074