Studies on human porin XXII: Cell membrane integrated human porin channelsare involved in regulatory volume decrease (RVD) of HeLa cells

Cell volume regulation receives increasing attention not only as the basis of regulatory volume increase or regulatory volume decrease (RVD) of cells in surroundings of changing osmolarity, but also appears to be relevant in cell proliferation, differentiation, and apoptosis. A central event in RVD is the opening of a volume-sensitive chloride/anion channel(s), and blockin g this pathway mould abolish RVD, This is shown here with monoclonal mouse anti-human type-1 porin antibodies, proving that porin is involved in this process. HeLa cells preincubated with these antibodies dramatically increas e their volume within about 1 min after a hypotonic stimulus by 70 mM NaCl Ringer solution, but do not move back toward their starting volume, thus in dicating abolished RVD. Corresponding effects are induced by the establishe d anion channel inhibitor DIDS. Video camera monitoring of cell size over t ime was used as a direct and noninvasive approach. We had already accumulat ed evidence that plasmalemma integrated eukaryotic porin channels form chlo ride/anion channels in this cell compartment and that they are involved in cell volume regulation. Finally, the present data again demonstrate the sui tability of our anti-porin antibodies in physiological studies. (C) 2000 Ac ademic Press.