Premium
Phospholipase A 2 Stimulation by Methyl Mercury in Neuron Culture
Author(s) -
Verity M. A.,
Sarafian T.,
Pacifici E. H. K.,
Sevanian A.
Publication year - 1994
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 - 10.1046/j.1471-4159.1994.62020705.x
Subject(s) - chemistry , phosphatidylinositol , arachidonic acid , phospholipid , phosphatidylcholine , biochemistry , phospholipase a2 , stimulation , endocrinology , biology , enzyme , membrane , kinase
In primary prelabeled cultures of cerebellar granule cells, methyl mercury (MeHg) induced a concentration‐ and time‐dependent release of [ 3 H]arachidonic acid. MeHg‐induced [ 3 H]arachidonate release was partially dependent on the extracellular Ca 2+ concentration. MeHg at 10–20 µ M also stimulated basal 45 Ca 2+ uptake after 20 min of incubation at 37°C, and at 10 µ M inhibited K + depolarization‐stimulated uptake. MeHg stimulated [ 3 H]arachidonate uptake, but had no effect on the rate of phospholipid reacylation. Phospholipase A 2 (PLA 2 ) activation preceded cytotoxicity, but at higher concentrations of MeHg such dissociation was not evident. Inhibition of MeHg‐induced PLA 2 activation by 100 µ M mepacrine failed to modify cytotoxicity. MeHg‐induced lipoperoxidation, measured as the production of thiobarbituric acid‐reacting products, was inhibited by α‐tocopherol without inhibition of [ 3 H]arachidonate release. The absence of α‐tocopherol inhibition of MeHg‐induced arachidonate release precludes a causal role for lipoperoxide‐induced PLA 2 activation in this system. Moreover, MeHg induced an increased susceptibility of unilamellar vesicles to exogenous PLA 2 in the presence of low Ca 2+ concentrations without evidence of lipid peroxidation. [ 3 H]Arachidonate incorporation into granule neuron phospholipids was analyzed by isocratic HPLC analysis. Relatively high proportional incorporation was found in the combined phosphatidylcholine fractions and phosphatidylinositol. With MeHg, an increase in the relative specific activity of incorporation was found in the phosphatidylinositol fraction, indicating a preferential turnover in this phospholipid species in the presence of MeHg.