The immunofluorescence approach, the confocal microscopy and the patch-clamp technique were used to investigate the expression of ClC-3 (one of the candidates of volume-activated chloride channels) and its relationships with the volume-activated chloride current and the capacity of regulatory volume decrease (RVD) in the cell cycle of nasopharyngeal carcinoma cells (CNE-2Z cells). The results indicated that CNE-2Z cells expressed ClC-3. ClC-3 was located predominantly inside the cells but not in the membrane. Both the expression level and the distribution of ClC-3 were cell cycle dependent. ClC-3 expression was low in G1 but high in S phase. The cells in G2/M phase possessed an intermediate level of the expression. ClC-3 expression level was negatively correlated to the RVD capacity and amplitude of the volume-activated chloride current in the cell cycle. The results suggest that ClC-3 may be an important factor in the regulation of cell cycle progression, but that it is probably not the chloride channel associated with RVD in these cancer cells.
Adenosine Triphosphate ; pharmacology ; Cell Cycle ; physiology ; Chloride Channels ; metabolism ; physiology ; Chlorides ; metabolism ; Gene Expression Regulation, Neoplastic ; Humans ; Muscle Proteins ; metabolism ; physiology ; Nasopharyngeal Neoplasms ; genetics ; metabolism ; pathology ; Tumor Cells, Cultured

The role of multidrug resistance (MDR1) gene in the activation of volume-activated chloride currents in bovine pigmented ciliary epithelial (PCE) cells was investigated by the patch-clamp technique, the antisense approach, the immunofluorescent technique and the confocal microscopy. PCE cells express P-glycoprotein (P-gp, the product of MDR1 gene). An MDR1 antisense oligonucleotide suppressed MDR1 expression (93% reduction of P-gp immunofluorescence), delayed the activation of a volume-activated chloride current (latency prolonged by 109%), reduced the activation rate by 62% and decreased the peak value of the current by 56%. The transfection reagent lipofectin and the mismatch control oligonucleotide did not significantly affect the current. The data indicate that the volume-activated chloride current is associated with the endogenous expression of MDR1 gene in PCE cells.
ATP-Binding Cassette, Sub-Family B, Member 1 ; biosynthesis ; Animals ; Cattle ; Cells, Cultured ; Chloride Channels ; physiology ; Ciliary Body ; cytology ; physiology ; Epithelial Cells ; metabolism ; physiology ; Gene Expression ; drug effects ; Genes, MDR ; physiology ; Oligonucleotides, Antisense ; pharmacology

Whole-cell patch clamp and cell volume measurement techniques were used to investigate the ATP-activated chloride current and the ATP effect on cell volume in nasopharyngeal carcinoma cells. Extracellular application of ATP in micromolar concentrations activated a current with the properties of modest outward rectification and negligible time-dependent inactivation in a dose-dependent manner. The current reversed at a potential [(-0.05+/-0.03) mV] close to the Cl- equilibrium potential (-0.9 mV). Substitution of Cl- with gluconate in the extracellular solution decreased the ATP-activated current and shifted the reversal potential positively. NPPB, one of the chloride channel blockers, inhibited the current by (81.03+/-9.36)%. The current was also depressed by the P2Y purinoceptor antagonist, reactive blue 2, by (67.39+/-5.06)%. ATP (50 micromol/L) decreased the cell volume under the isotonic condition. Depletion of extracellular and intracellular Cl- abolished the ATP effect on cell volume. The results suggest that extracellular ATP of micromolar scales can induce a chloride current associated with cell volume regulation by activation of chloride channel through binding to purinoceptor P2Y.
Adenosine Triphosphate ; physiology ; Cell Size ; drug effects ; Chloride Channels ; antagonists & inhibitors ; metabolism ; physiology ; Humans ; Nasopharyngeal Neoplasms ; metabolism ; pathology ; Nitrobenzoates ; pharmacology ; Patch-Clamp Techniques ; Tumor Cells, Cultured

The transwell chamber migration assay and the patch-clamp technique were used to investigate the volume-activated Cl(-) current (I(Cl.vol)) in migrated nasopharyngeal carcinoma cells (CNE-2Z). 47% hypotonic solution activated a ICl.vol in the migrated CNE-2Z cells. Compared with the control cells (non-migrated), the properties of this current and the sensitivity to Cl(-) channel blockers were changed. The current density in migrated CNE-2Z cells was higher than that in non-migrated cells. The current was almost completely inhibited by extracellular application of adenosine-5'-triphosphate (ATP, 10 mmol/L), 5-nitro-2-3-phenylpropylamino benzoic acid (NPPB, 100 mmol/L) and tamoxifen (30 mmol/L) in all voltage steps applied. The inhibition of NPPB and tamoxifen on the current was stronger in migrated cells than that in non-migrated cells. The permeability sequence of the four anions was Br(-)>Cl(-)> I (-)>Gluconate. The sequence was different from that of the non-migrated cells (I(-)> Br(-)> Cl(-)> Gluconate). The results suggest that volume-activated chloride channels may be involved in the CNE-2Z cell migration.
Carcinoma ; drug therapy ; metabolism ; pathology ; Cell Cycle ; drug effects ; physiology ; Cell Division ; drug effects ; Cell Movement ; drug effects ; Cell Size ; drug effects ; Chloride Channels ; antagonists & inhibitors ; metabolism ; physiology ; Chlorides ; metabolism ; Humans ; Nasopharyngeal Neoplasms ; drug therapy ; metabolism ; pathology ; Nitrobenzoates ; pharmacology ; Patch-Clamp Techniques ; Tamoxifen ; pharmacology ; Tumor Cells, Cultured