PHARMACOLOGY OF VOLUME REGULATION FOLLOWING HYPOTONICITY-INDUCED CELLSWELLING IN CLONAL N1E115 NEUROBLASTOMA-CELLS

When exposed to hypotonic solutions, clonal N1E115 neuroblastoma cells initially swell and later undergo a regulatory volume decrease (RVD). We studied the effects of a variety of transport inhibitors on the ti me course of cross-sectional area of N1E115 cells exposed to a solutio n of reduced osmolarity (pi = 186 mosm). Application to the bath of ei ther: (i) blockers of net K efflux through K channels (e.g. isotonic K Cl or 20 mM TEA); or (ii) blockers of net efflux through anion channel s (e.g. isotonic methanesulfonate, 10 mu M DIDS or 100 mu M IAA-94) al l prevent RVD. In contrast, ouabain (a Na+/K+ pump blocker), bumetanid e (a Na+/K+/Cl- cotransporter blocker) and SITS (a HCO3-/Cl- exchange blocker) do not. These data support the involvement of these channels over pumps or exchangers in solute exit during RVD. Only variable bloc k of RVD was achieved using blockers of stretch activated non-selectiv e cation C+(SA) channels (i.e., amiloride and gadolinium, Gd3+) or a m embrane permeant Ca chelator (BAPTA-AM) suggesting that neither the op ening of C+(SA) channels nor a global rise in cytosolic Ca2+ is critic al for triggering RVD.