Hypotonicity and ethanol modulate BK channel activity and chloride currents in GH4/C1 pituitary tumour cells.
OBJECTIVE
Description of the effects of hypotonic cell swelling and ethanol on maxi Ca2+-activated K+ channel (BK channel) activity and Cl- channel activity in GH4/C1 pituitary tumour cells.


METHODS
Whole cell-, cell attached- and outside-out patch clamp measurements, fluorescence (fluo-3) measurements of intracellular Ca2+ concentration, cell size video monitoring.


RESULTS
GH4/C1 pituitary tumour cells respond to both hypotonicity and ethanol with cell swelling which is followed by a regulatory volume decrease (RVD). Tetraethylammonium and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) induced cell swelling per se and inhibited hypotonicity induced RVD. Ethanol-induced swelling is paralleled by an increase in the intracellular Ca2+ concentration and augmented by DIDS. BK channel activation by hypotonicity and ethanol is demonstrated in patch clamp experiments both in intact cells (cell attached configuration) and a subset of excised membrane patches (outside-out configuration). Cell swelling and addition of ionomycin under isotonic conditions leads to the activation of outwardly rectifying Cl- currents with time dependent activation at positive potentials.


CONCLUSIONS
In GH4/C1 cells both hypotonicity and ethanol lead to cell swelling, RVD and to activation of BK channels. The hypotonicity-induced BK channel activation can also be observed in cell free outside-out patches. Hypotonicity, but not ethanol leads to the activation of Cl- channels with features of Ca2+-activated Cl- currents.
Jakab
M
M
Institute of Physiology and Pathophysiology, Paracelsus Private Medical University Salzburg, Salzburg, Austria.
Schmidt
S
S
Grundbichler
M
M
Paulmichl
M
M
Hermann
A
A
Weiger
T
T
Ritter
M
M
D016475:3T3 Cells; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D048429:Cell Size; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D018118:Chloride Channels / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology*; D051379:Mice; D018715:Microscopy, Video; D018408:Patch-Clamp Techniques; D010911:Pituitary Neoplasms / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D019789:Tetraethylammonium / Q000494:pharmacology
D002492:Central Nervous System Depressants; D018118:Chloride Channels; D007038:Hypotonic Solutions; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D000431:Ethanol; D019789:Tetraethylammonium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium