Small-conductance Cl- channels in rabbit parietal cells activated by prostaglandin E2 and inhibited by GTP gamma S.
1. Small-conductance, sub-picosiemens (sub-pS) Cl- channels in the basolateral membrane of non-stimulated parietal cells in isolated rabbit gastric glands were studied by whole-cell patch-clamp and noise analysis techniques. 2. Voltage-independent whole-cell Cl- currents were recorded from parietal cells equilibrated with Cl(-)-containing solutions. Intracellular application of guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S, 5-200 microM) slowly decreased the whole-cell Cl- current, and its steady-state effect was observed about 6 min after the start of the dialysis. The half-maximal inhibitory concentration of GTP gamma S was about 60 microM. 3. The single Cl- channel conductance was estimated to be 0.37 pS from the variance noise analysis during the GTP gamma S-induced inhibitory process of the whole-cell Cl- current. It is in agreement with the value obtained by a method of power spectrum analysis (0.47 pS). 4. The whole-cell Cl- current was increased by prostaglandin E2 (10 microM). The increased Cl- current was reduced by the subsequent application of GTP gamma S (50 microM), whereas the GTP gamma S (50 microM)-induced inhibition of the Cl- current was not reversed by the subsequent application of prostaglandin E2 (10 microM). 5. The combined intracellular application of GTP gamma S (50 microM) and GDP beta S (500 microM) markedly reduced the inhibitory effect of GTP gamma S, indicating that a GTP-binding protein is involved in the regulation of the Cl- channel. 6. Treatment of parietal cells with pertussis toxin (PTX, 500 ng/ml) for 90-140 min did not affect the GTP gamma S-induced inhibition of the whole-cell Cl- current. 7. Intracellular application of cyclic AMP-dependent protein kinase inhibitor peptide (100 micrograms/ml) or 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) (5 mM, pCa 8) did not affect the GTP gamma S-induced inhibition of the whole-cell Cl- current. 8. The present study has suggested that the opening of the sub-pS Cl- channel is modulated negatively by a PTX-insensitive GTP-binding protein and positively by prostaglandin E2.
Sakai
H
H
Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
Takeguchi
N
N
D000818:Animals; D002478:Cells, Cultured; D002713:Chlorine / Q000378:metabolism*; D015232:Dinoprostone / Q000502:physiology*; D004594:Electrophysiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000502:physiology*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000502:physiology; D008297:Male; D010295:Parietal Cells, Gastric / Q000378:metabolism*; D011817:Rabbits; D013873:Thionucleotides / Q000502:physiology
D007473:Ion Channels; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002713:Chlorine; C023427:guanosine 5'-O-(2-thiodiphosphate); D015232:Dinoprostone