Activation of Ca(2+)-dependent K+ channel and Cl- conductance in canine pancreatic acinar cells through a cyclic AMP pathway.
Effects of adenosine 3',5'-cyclic monophosphate (cAMP) on Ca(2+)-dependent K+ channel and Cl- conductance in the plasma membrane of isolated canine pancreatic acinar cells were studied by patch-clamp methods. In whole-cell current recordings on isolated cells dialyzed with K(+)-rich solution containing 0.5 mM EGTA, addition of 0.5 mM dibutyryl cAMP (dbcAMP), or 50 microM forskolin to the bath increased outward K+ and inward Cl- currents associated with depolarizing and hyperpolarizing voltage jumps, respectively. In intact cells (cell-attached configurations), addition of 0.5 mM dbcAMP or 50 microM forskolin to the bath increased the opening of single K+ channel. In Ca(2+)-free external solution (bath and pipette) 50 microM forskolin or 0.5 mM dbcAMP application evoked an increase in the opening of single K+ channel in intact cells. Addition of 0.5 mM dbcAMP to the bath solution containing 10 mM EGTA without Ca2+ increased the currents of whole-cell dialyzed with K(+)-rich solution containing 10 mM EGTA. When cell was dialyzed with 20 mM EGTA, dbcAMP, or forskolin application did not increase the whole-cell currents. In excised inside-out patches, addition of the catalytic subunit of cAMP-dependent protein kinase (16 U/ml) in the presence of 0.3 mM ATP to the cytoplasmic face of membrane activated the K+ channel, but 0.1 mM cAMP did not. These results suggest that cAMP-dependent phosphorylation can activate Ca(2+)-dependent K+ channels without increase in intracellular free Ca2+ and cAMP-dependent mechanism can activate Ca(2+)-dependent Cl- conductances without the increase in Ca2+ in canine pancreatic acinar cells.
Suzuki
K
K
Department of Physiology, Tokai University School of Medicine, Isehara, Japan.
Onoe
K
K
Takahira
H
H
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D004285:Dogs; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011494:Protein Kinases / Q000494:pharmacology
D002712:Chlorides; D015221:Potassium Channels; D005576:Colforsin; D004533:Egtazic Acid; D003994:Bucladesine; D000242:Cyclic AMP; D011494:Protein Kinases; D002118:Calcium