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Title: The role of the large conductance Ca²⁺-activated K⁺ channel in adenosine receptor-mediated cytoprotection
Author: Fretwell, Laurice V.
ISNI:       0000 0004 2678 3701
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 2009
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The rat embryonic cardiomyoblast-derived H9c2 cell line is increasingly used for studies into cardioprotection, as these cells display similar properties to primary cardiomyocytes. Adenosine receptors are well known mediators of cardioprotection and trigger effectors such as the mitochondrial KATP channel – however, the role of the mitochondrial BKCa channel in adenosine receptor-mediated cardioprotection has not been investigated. GPCR assays provided evidence for functional expression of Gi-coupled adenosine A₁ and κ-opioid receptors, Gs-coupled β₂ adrenergic receptors and Gq-coupled UTP-binding P2Y purinergic receptors on H9c2 cells. Activation of the adenosine A₁ receptor with CPA (N(6)-cyclopentyladenosine) provided significant protection against hypoxia-induced cell death in these cells, as did opening of a BKCa channel with NS1619. The location of this BKCa channel was confirmed to be the mitochondria by the probing of subcellular fractions with BKCa-specific antibodies. Interestingly, CPA-induced protection against hypoxia was blocked by inhibition of the BKCa channel. In a model of hypoxia/reoxygenation in H9c2 cells both CPA and NS1619 significantly reduced cell death when used as postconditioning agents, and in both cases the protection was abolished by blockade of the BKCa channel. This data suggests for the first time that, in H9c2 cells, the BKCa channel is involved in A₁ receptor-mediated cytoprotection. To confirm this finding in a more physiologically relevant model – and validate the use of H9c2 cells as a model for cardioprotection – hypoxia/reoxygenation in isolated rat ventricle strips was investigated. It was discovered that blockade of the BKCa channel significantly attenuated protection afforded by hypoxia preconditioning and preconditioning triggered by activation of the adenosine A₁ and A₂A receptors. For the first time, this report has shown an important role for the BKCa channel in adenosine receptor-mediated cytoprotection.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available