ISSN:
1432-2013
Keywords:
Key words Smooth muscle
;
Cell volume
;
Chloride current
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The characteristics of volume-sensitive chloride current (I Cl) 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 I Cl was effectively inhibited by the Cl– channel blockers, 4,4′-diisothiocyanatostilbene-2,2’-disulphonic acid (DIDS, 100 μM), and niflumic acid (10 μM). DIDS suppressed outward current more effectively than inward current. Also, the I Cl 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 I Cl 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 I Cl 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 (I Cl) is present in guinea-pig gastric myocyte and the I Cl may play a role in smooth muscle cell volume regulation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050478
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