SWELLING-INDUCED CHLORIDE CURRENTS IN NEUROBLASTOMA-CELLS ARE CALCIUM-DEPENDENT

Abstract

The effects of osmotic stress on chloride (Cl-) currents in the human neuroblastoma cell line CHP-100 were evaluated, Following exposure to hypoosmotic solution, an increase in whole-cell Cl- current was observed, This current was blocked by the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), In cells loaded with the Cl- permeability marker (125)l, exposure to hypoosmotic solution increased (125)l efflux by 197 +/- 14% (n = 41, p <0.05) over controls, This increase was sensitive to NPPB, Hypoosmotic stress also increased cytosolic calcium levels (Ca2+) in fura-2-loaded cells, Pretreatment with EGTA inhibited the increase in cytosolic Ca2+, (125)l efflux, and whole-cell Cl- current produced by hypoosmotic solution. Antagonists of N-, L-, and T-type Ca2+ channels did not alter stimulation in (125)l efflux or cytosolic Ca2+ levels during osmotic stress, However, omega-conotoxin MVIIC, a P-type Ca2+ channel blocker, inhibited hypoosmotically activated whole-cell Cl- currents and increases in cytosolic Ca2+, It is concluded that a Ca2+-dependent change in Cl- permeability is activated in CHP-100 cells in response to osmotic stress.