Heparin uncouples the muscarinic receptors from GK protein in the atrial cell membrane of the guinea-pig heart

• Published in: Pflügers Archiv 1990-09, Vol.417 (1), p.126-128
• Main Authors: ITO, H, TAKIKAWA, R, IGUCHI, M, HAMADA, E, SUGIMOTO, T, KURACHI, Y
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Dose-Response Relationship, Drug; Fundamental and applied biological sciences. Psychology; GTP-Binding Proteins - metabolism; GTP-Binding Proteins - physiology; Guinea Pigs; Heart; Heart Atria - cytology; Heart Atria - metabolism; Heart Atria - ultrastructure; Heparin - pharmacology; Potassium Channels - drug effects; Potassium Channels - physiology; Receptors, Muscarinic - drug effects; Receptors, Muscarinic - metabolism; Vertebrates: cardiovascular system
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/BF00370783

The effects of heparin on activation of the G protein-gated muscarinic K+ channel were examined in atrial cells of guinea-pig heart. The inside-out patch clamp technique was used. The pipette solution contained 1.1 microM acetylcholine (ACh). In the inside-out patches, intracellular GTP activated the muscarinic, K+ channel. When heparin (0.05-5 units/ml) was further added to the intracellular side of the patch membrane, the channel openings were depressed in a concentration-dependent fashion. The effects of heparin were reversible after wash-out. Heparin did not affect GTP-gamma S-induced activation of the K+ channel. Therefore, it is suggested that heparin may uncouple the muscarinic receptors from GK protein in the cardiac atrial cell membrane.