Ion Fluxes through KCa2 (SK) and Cav1 (L-type) Channels Contribute to Chronoselectivity of Adenosine A1 Receptor-Mediated Actions in Spontaneously Beating Rat Atria
| Autor: | A.P. Fontes‐Sousa, Pedro A. Lima, Miguel Faria, Nádia Oliveira-Monteiro, Paulo Correia-de-Sá, Bruno Bragança, Fátima Ferreirinha |
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| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
negative chronotropism and inotropism 030204 cardiovascular system & hematology Pharmacology Apamin SK channel 03 medical and health sciences Adenosine A1 receptor chemistry.chemical_compound 0302 clinical medicine medicine Pharmacology (medical) G protein-coupled inwardly-rectifying potassium channel Original Research Sinoatrial node Chemistry lcsh:RM1-950 L-type voltage-sensitive calcium channels Hyperpolarization (biology) potassium channels Adenosine Potassium channel 030104 developmental biology medicine.anatomical_structure lcsh:Therapeutics. Pharmacology adenosine atria Biophysics medicine.drug |
| Zdroj: | Frontiers in Pharmacology Frontiers in Pharmacology, Vol 7 (2016) |
| ISSN: | 1663-9812 |
| DOI: | 10.3389/fphar.2016.00045 |
| Popis: | Impulse generation in supraventricular tissue is inhibited by adenosine and acetylcholine via the activation of A1 and M2 receptors coupled to inwardly rectifying GIRK/KIR3.1/3.4 channels, respectively. Unlike M2 receptors, bradycardia produced by A1 receptors activation predominates over negative inotropy. Such difference suggests that other ion currents may contribute to adenosine chronoselectivity. In isolated spontaneously beating rat atria, blockade of KCa2/SK channels with apamin and Cav1 (L-type) channels with nifedipine or verapamil, sensitized atria to the negative inotropic action of the A1 agonist, R-PIA, without affecting the nucleoside negative chronotropy. Patch-clamp experiments in the whole-cell configuration mode demonstrate that adenosine, via A1 receptors, activates the inwardly-rectifying GIRK/KIR3.1/KIR3.4 current resulting in hyperpolarization of atrial cardiomyocytes, which may slow down heart rate. Conversely, the nucleoside inactivates a small conductance Ca(2+)-activated KCa2/SK outward current, which eventually reduces the repolarizing force and thereby prolong action potentials duration and Ca(2+) influx into cardiomyocytes. Immunolocalization studies showed that differences in A1 receptors distribution between the sinoatrial node and surrounding cardiomyocytes do not afford a rationale for adenosine chronoselectivity. Immunolabelling of KIR3.1, KCa2.2, KCa2.3, and Cav1 was also observed throughout the right atrium. Functional data indicate that while both A1 and M2 receptors favor the opening of GIRK/KIR3.1/3.4 channels modulating atrial chronotropy, A1 receptors may additionally restrain KCa2/SK activation thereby compensating atrial inotropic depression by increasing the time available for Ca(2+) influx through Cav1 (L-type) channels. |
| Databáze: | OpenAIRE |
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