Role of G proteins in the acetylcholine-induced potassium current of canine atrial cells

• Published in: The American journal of physiology Vol. 257; no. 5 Pt 2; p. H1516
• Main Authors: Sorota, S, Hoffman, B F
• Format: Journal Article
• Language: English
• Published: United States 01.11.1989
• Subjects: Acetylcholine - pharmacology; Animals; Cells, Cultured; Dogs; Electrophysiology; GTP-Binding Proteins - pharmacology; GTP-Binding Proteins - physiology; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Triphosphate - pharmacology; Heart Atria; Myocardium - cytology; Myocardium - metabolism; Potassium Channels - drug effects; Potassium Channels - metabolism; Potassium Channels - physiology; Thionucleotides - pharmacology
• ISSN: 0002-9513
• DOI: 10.1152/ajpheart.1989.257.5.H1516

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.