Volume-sensitive chloride current activated by hyposmotic swelling in antral gastric myocytes of the guinea-pig.
The characteristics of volume-sensitive chloride current (ICl) induced by osmotic cell swelling were studied using the whole-cell patch-clamp technique and cell diameters of antral circular guinea-pig myocytes were simultaneously measured under isosmotic and hyposmotic conditions by using a video image analysis system. At -60 mV, osmotic cell swelling (200 mosmol/l) activated a sustained inward current. Instantaneous current/voltage (I-V) relations obtained by step voltage pulses showed an outward rectification. At potentials above +40 mV, the current exhibited time-dependent decay. The outward current amplitude was decreased and the reversal potential was shifted to more positive potentials by replacement of external Cl- with gluconate-, while the current amplitude and the I/V relation were not affected by replacing extracellular Na+ with N-methyl-D-glucamine. The anion permeability sequence of the swelling-induced current was I- (1.80) > Br- (1.31) > Cl- (1) > F- (0.85) > gluconate- (0.18). The ICl was effectively inhibited by the Cl- channel blockers, 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS, 100 microM), and niflumic acid (10 microM). DIDS suppressed outward current more effectively than inward current. Also, the ICl was dose-dependently inhibited by arachidonic acid, an unsaturated fatty acid and also inhibited by other unsaturated fatty acids (linoleic acid and oleic acid) but not by stearic acid, a saturated fatty acid. The inhibitory effect of arachidonic acid on ICl was not prevented by indomethacin, a cyclo-oxygenase inhibitor and chelerythrine, a protein kinase C inhibitor. Under whole-cell patch-clamp conditions, the cell diameter was continuously measured using video image analysis, which reflects the change in cell volume. A hyposmotic-stimulation-induced increase of cell diameter was followed by ICl activation. In intact single gastric myocytes, relatively severe hyposmotic (176 mosmol/l) superfusing solution increased the cell diameter and the pretreatment with DIDS or with niflumic acid significantly potentiated the above effect of hyposmotic superfusion. These results suggest that volume-sensitive outwardly rectifying chloride current (ICl) is present in guinea-pig gastric myocyte and the ICl may play a role in smooth muscle cell volume regulation.
Xu
W X
WX
Department of Physiology and Biophysics, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Korea.
Kim
S J
SJ
So
I
I
Kang
T M
TM
Rhee
J C
JC
Kim
K W
KW
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D002463:Cell Membrane Permeability; D048429:Cell Size; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004553:Electric Conductivity; D005260:Female; D005942:Gluconates; D006168:Guinea Pigs; D006801:Humans; D007038:Hypotonic Solutions; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology*; D009544:Niflumic Acid / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011706:Pyloric Antrum / Q000166:cytology*; D012965:Sodium Chloride
D018118:Chloride Channels; D016861:Cyclooxygenase Inhibitors; D005942:Gluconates; D007038:Hypotonic Solutions; D016718:Arachidonic Acid; D012965:Sodium Chloride; D009544:Niflumic Acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C030691:gluconic acid