ATP is not required for anion current activated by cell swelling in multidrug-resistant lung cancer cells.
During whole cell recording with 4 mM ATP and 0.1 mM GTP in the pipette, outwardly rectifying Cl- currents (155 +/- 20.5 pA/pF) were repetitively activated on reduction of bath solution osmolarity from 290 mosM (control) to 210 mosM. These currents were sensitive to 0.1-1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Omission of ATP from the pipette solution reduced the current magnitude to 42.7 +/- 9.5 pA/pF and prevented repetitive activation. More hyposmotic solutions (160 mosM) usually elicited current repetitively despite an ATP-free pipette solution. In cells depleted of ATP (to < 5% of control) by preincubation with 2-deoxyglucose (10 mM) and rotenone (100 nM), hyposmotic solutions failed to activate significant current. Cell volume increased to 230 +/- 18% of control (19.1 +/- 1.2 microns) in 210 mosM bath (normal cells) but only to 114 +/- 13% of control in ATP-depleted cells exposed to 160 mosM solution. This failure of ATP-depleted cells to swell in hypotonic external solutions was reversed by overnight pretreatment with cytochalasin D (2 micrograms/ml; n = 6) but not by colchicine (250 microM; n = 8). In outside-out patches of membrane dialyzed with zero ATP and excised from swollen cells, we observed sustained activation of a 53-pS outwardly rectifying channel (chord conductance, +100 mV; open probability approximately 1.0). In cell-attached patches from normal and ATP-depleted cells, we activated similar channels by suction. ATP does not appear to be an absolute requirement for the activation of this Cl- channel in H69AR cells but may be essential for the normal volume response and channel activation mediated through cytoskeletal elements within cells.
Jirsch
J D
JD
Department of Physiology, Queen's University, Kingston, Canada.
Loe
D W
DW
Cole
S P
SP
Deeley
R G
RG
Fedida
D
D
D000255:Adenosine Triphosphate / Q000502:physiology*; D000838:Anions / Q000378:metabolism*; D018288:Carcinoma, Small Cell / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D018118:Chloride Channels / Q000502:physiology; D004351:Drug Resistance; D004553:Electric Conductivity; D004594:Electrophysiology; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D009995:Osmosis; D014407:Tumor Cells, Cultured
D000838:Anions; D018118:Chloride Channels; D000255:Adenosine Triphosphate