Role of G proteins in the acetylcholine-induced potassium current of canine atrial cells.
The acetylcholine-induced opening of potassium channels depends on GTP-binding proteins in the chick, guinea pig, frog, and rat. In contrast, Bubien and Woods (Biochem. Biophys. Res. Commun. 142: 1039-1045, 1987) have recently postulated that the acetylcholine response in cultured canine atrial cells may be independent of GTP-binding proteins. In whole cell patch-clamp experiments using cultured canine atrial cells, we did not detect an effect of GTP (10(-4) M) in the pipette solution on the acetylcholine-induced potassium current. However, 500 microM guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) in the pipette diminished the response to acetylcholine. Pertussis toxin (30 ng/ml for 24 h) blocked the response to acetylcholine. With guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 3 microM) in the patch pipette, acetylcholine irreversibly increased membrane conductance. The current-voltage relationship for the persistently activated current was similar to that induced by acetylcholine. We conclude that the acetylcholine-induced potassium current in canine atrial cells behaves like that seen in other species and depends on GTP-binding proteins.
Sorota
S
S
Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Hoffman
B F
BF
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004285:Dogs; D004594:Electrophysiology; D019204:GTP-Binding Proteins / Q000494:pharmacology / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000494:pharmacology; D006325:Heart Atria; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology
D015221:Potassium Channels; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D000109:Acetylcholine