Control of cell proliferation by cell volume alterations in rat C6 glioma cells

K+ and Cl- channels ale involved in regulating the proliferation of a numbe r of cell types. Two main hypotheses have been proposed to explain the mech anism by which these channels influence cell proliferation: regulation of m embrane potential and regulation of cell volume. In order to test these hyp otheses, we measured, under different experimental conditions, the volume, membrane potential and rate of proliferation of C6 glioma cells. Cells cult ured in control medium for 1-4 days were compared with cells cultured for t he same period of time in the presence of broad spectrum channel blockers: tetraethylammonium, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and Cs+, in hypertonic media (29% increased osmolarity with NaCl, KCl or sucro se), in hypotonic medium (23%, decreased osmolarity with H2O) or in the pre sence of the specific channel blockers, i.e. mast cell degranulating peptid e, charybdotoxin or chlorotoxin. In all of these conditions, we observed a close correspondence between the rate of proliferation and the mean cell vo lume. The proliferation decreased when volume increased. Moreover, whereas control cells were flattened, spindle-shaped, bipolar or multipolar, cells cultured in media supplemented with NPPB, KCI or CsCl were round with few p rocesses. Of the agents tested, only KCI and Cs+ depolarized the cells. The se results show that alterations of the rate of proliferation by K+ and Cl- channel blockers or anisotonia are closely related with changes in cell vo lume or form but are not correlated with changes in membrane potential.