KUPFFER CELLS CONTAIN A GLYCINE-GATED CHLORIDE CHANNEL

Here the effect of glycine on intracellular Ca2+ concentration ([Ca2+] (i)) in cultured Kupffer cells stimulated with lipopolysaccharide (LPS ) was investigated to assess the possibility that they contain a glyci ne-gated chloride channel. LPS (10 mu g/ml) increased [Ca2+](i) rapidl y, with peak values reaching 307 +/- 29 nM. Glycine (1 mM) prevented t his increase nearly completely. Low concentrations of strychnine (1 mu M), a glycine receptor antagonist, reversed the inhibitory effect of glycine completely; however, high concentrations of strychnine (1 mM) mimicked glycine. The effects of glycine and high-dose strychnine were prevented when cells were incubated in chloride-free buffer. Furtherm ore, potassium (25 mM) and LPS depolarized the Kupffer cell plasma mem brane, whereas glycine caused hyperpolarization and prevented depolari zation due to potassium and LPS. Moreover, tumor necrosis factor-alpha (TNF-alpha) production in cultured Kupffer cells due to LPS was decre ased significantly by glycine. Therefore, it is concluded that Kupffer cells contain a glycine-gated chloride channel similar to that descri bed previously in the central nervous system. Prevention of increases in [Ca2+](i) due to LPS by activation of chloride influx reduced synth esis and release of toxic mediators by Kupffer cells.