K-INDUCED MAMMALIAN NEUROBLASTOMA CELL SWELLING - A POSSIBLE MECHANISM TO INFLUENCE PROLIFERATION( CHANNEL BLOCK)

1. A variety of studies hare suggested that K+ channel activity is a k ey determinant for cell progression through the G1 phase of mitosis. W e have previously proposed that K+ channels control the activity of ce ll cycle-regulating proteins via regulation of cell volume. In order t o test this hypothesis, we measured, with a Coulter counter and under different experimental conditions, the volume and rate of proliferatio n of neuroblastoma x glioma hybrid NG108-15 cells. 2. The K+ channel b lockers TEA (1-10 nM), 4-aminopyridine (0.2-2 mM) and Cs+ (2.5-10 mM) increased the cell volume and decreased the rate of cell proliferation . Proliferation was fully inhibited when cell volume was increased by 25 %.3. A 40 % increase in the culture medium osmolarity With NaCl ind uced a 25 % increase in cell volume and an 82 % decrease in the rate o f cell proliferation. A 40 % increase in the culture medium osmolarity with mannitol induced a 9 % increase in cell volume and a 60 % decrea se in the rate of cell proliferation.4. The Cl- channel blocker NPPB ( 5-nitro-2-(3-phenylpropylamino) benzoic acid; 50 mu M) induced a 12 % increase in cell volume and a 77 % decrease in the rate of cell prolif eration. 5. A 24 % reduction in the culture medium osmolarity with H2O induced a 21 % decrease in cell volume and a 32 % increase in the rat e of cell proliferation. 6. Under whole-cell patch-clamp conditions, a ntibiotics (penicillin plus streptomycin) decreased the voltage-depend ent K+ current. Omission of antibiotics from the culture medium induce d a 10 % decrease in the cell volume and a 32 % increase in the rate o f cell proliferation. 7. These results suggest that the mechanisms con trolling cell proliferation are strongly influenced by the factors whi ch deter mine cell volume. This could take into account the role in mi togenesis of K+ channels and of other ionic pathways involved in cell volume regulation.