INTRACELLULAR LUCIFER-YELLOW LEAKAGE FROM NOVIKOFF CELLS IN THE PRESENCE OF ATP OR LOW EXTRACELLULAR CA - EVIDENCE FOR HEMI-GAP JUNCTION CHANNELS

Lucifer Yellow was microinjected into Novikoff hepatoma cells and leak age was investigated under treatment with ATP (5 mM) and EGTA (5 mM) i n the culture medium. In control conditions there was no leakage in si ngle or paired cells, except a few cases which showed very slow leakag e (defined as slope < -0.0007/sec). Slow leakage rate (slope > -0.0008 but < -0.009/sec) and quick leakage rate (slope > -0.01) of intracell ular dye were not seen. Dye transfer between cell pairs after Lucifer Yellow was injected into one cell was divided into two groups: quick t ransfer rates (4 cases, slope = -0.151 +0.0032) and slow transfer rate s (15 cases, slope = -0.041 +0.0018). Under ATP treatment the intracel lular dye leakage was observed in single cells (16 of 31 cases) and in cell pairs (20 of 57 cases). Extracellular low Ca2+ (EGTA treatment) enhanced the dye leakage much more: 30 of 40 cases in single cells and 21 of 36 cases in cell pairs. The leakage rates of intracellular dye under these treatments were similar to the transfer rates of the the d ye between cell pairs with quick and slow rates. It is suggested that the dye leakage from Novikoff cells under treatment with ATP or low (C a2+](0) shares the same mechanism as dye transfer through gap junction s, suggesting that the hemichannels in the plasma membrane can be open ed under certain conditions.