Lysophosphatidylcholine Induces Taurine Release from HeLa Cells |
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Authors: | IH Lambert B Falktoft |
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Institution: | The August Krogh Institute, Biochemical Department, Universitetsparken 13, DK-2100, Copenhagen O, Denmark. |
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Abstract: | The putative role of lysophospholipids in activation and regulation of the volume-sensitive taurine efflux was investigated
in HeLa cells using tracer technique. Lysophosphatidylcholine (LPC, 10 μm) with oleic acid increased taurine efflux during hypotonic and isotonic conditions. Substituting palmitic or stearic acid
for oleic acid enhanced taurine release during isotonic conditions, whereas ethanolamine, serine or inositol containing lysophospholipids
were ineffective. High concentrations of LPC (25 μm) induced Ca2+ influx, loss of adenosine nucleotides, taurine and the Ca2+-sensitive probe Fura-2, and thus reflected a general breakdown of the membrane permeability barrier. Low concentrations of
LPC (5–10 μm) solely induced taurine efflux. The LPC-induced taurine release was unaffected by anion channel blockers (DIDS, MK196) and
the 5-lipoxygenase inhibitor ETH 615-139, which all blocked the volume sensitive taurine efflux. Furthermore, LPC-induced
taurine release was reduced by antioxidants (NDGA, vitamin E) and the protein tyrosine kinase inhibitor genistein. The swelling-induced
taurine efflux was in the absence of LPC unaffected by vitamin E, blocked by genistein, and increased by H2O2 and the protein tyrosine phosphatase inhibitor vanadate. It is suggested that low concentrations of LPC permeabilizes the
plasma membrane in a Ca2+-independent process that involves generation of reactive oxygen species and tyrosine phosphorylation, and that LPC is not
a second messenger in activation of the volume sensitive taurine efflux in HeLa cells.
Received: 17 December 1999/Revised: 13 April 2000 |
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Keywords: | : Cell volume regulation — Membrane permeabilization — Vitamin E — Tyrosine phosphorylation — Lysophospholipids |
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