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Alteration of cytosolic free calcium homeostasis by SIN‐1: high sensitivity of L‐type Ca 2+ channels to extracellular oxidative/nitrosative stress in cerebellar granule cells
Author(s) -
GutiérrezMartín Yolanda,
MartínRomero Francisco Javier,
Henao Fernando,
GutiérrezMerino Carlos
Publication year - 2005
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02964.x
Subject(s) - chemistry , extracellular , calcium , biophysics , cytosol , catalase , voltage dependent calcium channel , peroxynitrite , medicine , biochemistry , oxidative stress , superoxide , biology , enzyme , organic chemistry
Abstract Exposure of cerebellar granule neurones in 25 m m KCl HEPES‐containing Locke's buffer (pH 7.4) to 50–100 µ m SIN‐1 during 2 h decreased the steady‐state free cytosolic Ca 2+ concentration ([Ca 2+ ]i) from 168 ± 33 n m to 60 ± 10 n m , whereas exposure to ≥ 0.3 m m SIN‐1 produced biphasic kinetics: (i) decrease of [Ca 2+ ]i during the first 30 min, reaching a limiting value of 75 ± 10 n m (due to inactivation of L ‐type Ca 2+ channels) and (ii) a delayed increase of [Ca 2+ ]i at longer exposures, which correlated with SIN‐1‐induced necrotic cell death. Both effects of SIN‐1 on [Ca 2+ ]i are blocked by superoxide dismutase plus catalase and by Mn(III)tetrakis(4‐benzoic acid)porphyrin chloride. Supplementation of Locke's buffer with catalase before addition of 0.5–1 m m SIN‐1 had no effect on the decrease of [Ca 2+ ]i but further delayed and attenuated the increase of [Ca 2+ ]i observed after 60–120 min exposure to SIN‐1 and also protected against SIN‐1‐induced necrotic cell death. α‐Tocopherol, the potent NMDA receptor antagonist (+)‐MK‐801 and the N‐ and P‐type Ca 2+ channels blocker ω‐conotoxin MVIIC had no effect on the alterations of [Ca 2+ ]i upon exposure to SIN‐1. However, inhibition of the plasma membrane Ca 2+ ATPase can account for the increase of [Ca 2+ ]i observed after 60–120 min exposure to 0.5–1 m m SIN‐1. It is concluded that L‐type Ca 2+ channels are a primary target of SIN‐1‐induced extracellular nitrosative/oxidative stress, being inactivated by chronic exposure to fluxes of peroxynitrite of 0.5–1 μ m /min, while higher concentrations of peroxynitrite and hydrogen peroxide are required for the inhibition of the plasma membrane Ca 2+ ATPase and induction of necrotic cell death, respectively.