Three Different Potassium Channels in Human Atrium: Contribution to the Basal Potassium Conductance

• Published in: Circulation research Vol. 66; no. 5; pp. 1277 - 1286
• Main Authors: Heidbüchel, Hein, Vereecke, Johan, Carmeliet, Edward
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 01.05.1990; Lippincott
• Subjects: Acetylcholine - pharmacology; Adenosine Triphosphate - pharmacology; Animals; atrium; Biological and medical sciences; Electrophysiology; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Heart; Heart - physiology; Heart Atria; Humans; Ion Channel Gating; membrane conductance; Myocardium - cytology; Myocardium - metabolism; Potassium - physiology; Potassium Channels - drug effects; Potassium Channels - metabolism; Potassium Channels - physiology; Vertebrates: cardiovascular system; Heart; Human; Atrium; Electrophysiology; Ions; Patch clamp method; Ionic channel; Neuromediator; Acetylcholine; Cations; Circulatory system; Ionic conductance; Potassium; Heart cell
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.66.5.1277

We applied the cell-attached and inside-out patch-clamp technique under symmetrical isotonic potassium conditions on single human (and guinea pig) atrial cells. The human cells were isolated by a modified method to that described earlier. Our aim was twofold1) to study the single-channel characteristics of potassium channels in human atrial single cells, present under basal conditions (iKI and iK(ATP)) or when stimulated with 10 M acetylcholine; and 2) to calculate the contribution of these three channel types to the total basal potassium conductance in human atrial cells, and to compare the results with data on guinea pig atrial cells under the same conditions. We found that in human cells 58% of the patches (n=42/74) contained acetylcholine-sensitive potassium channelstheir conductance was 42±1.2 pS and mean open time (τo) was 1.7±0.5 msec. They showed sporadic openings in the absence of agonist, and activation by acetylcholine was G-protein dependent. In 16% of the patches (n=7/44), adenosine (10 M) activated the same channels, but the activity was lower than when stimulated by acetylcholine. In 18% of the patches (n=9/51), an iKI channel was present (conductance, 27 pS; τo, 8.7 msec), whereas in the cell-attached mode, ATP-dependent channels were never seen. However, they were present in half of the inside-out patches on washout of ATP1 (conductance, 73 pS; τo 1.4 msec). The basal potassium conductance (i.e., in the absence of any exogenous hormone or neurotransmitter) was mainly due to iKI channels in both human and guinea pig cells, a finding that is in contrast with previous reports. However, the potassium current that is induced by acetylcholine is much higher in guinea pig than in human isolated cells; a fraction of it would suffice to fully determine the resting potassium conductance in guinea pig atrial cells, whereas it can play only a modulatory role in human cells. This difference could be important in species-specific autonomic modulation and antiarrhythmic drug action.