Swelling-induced chloride currents in neuroblastoma cells are calcium dependent

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 ¹²⁵I, exposure to hypoosmotic solution increased ¹²⁵I 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⁺, ¹²⁵I efflux, and whole-cell Cl^- current produced by hypoosmotic solution. Antagonists of N-, L-, and T-type Ca²⁺ channels did not alter stimulation in ¹²⁵I efflux or cytosolic Ca²⁺ levels during osmotic stress. However, ω-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.