Direct evidence of chloride ion efflux in ischaemic and pharmacological preconditioning of cultured cardiomyocytes.

Aims: We have previously shown that reduction of ischaemic cell swelling via enhanced cell volume regulation is a key mechanism of ischaemic preconditioning (IPC) in cardiomyocytes. We have also shown that pharmacological blockade of Cl− channels abolishes cardioprotection achieved by IPC in Langendorff-perfused hearts and freshly isolated cardiomyocytes, thus suggesting that Cl− plays a key role in IPC cardioprotection. However, direct evidence of Cl− channel activation resulting in transsarcolemmal Cl− efflux by IPC had been lacking. To address this issue, 24 h cultured rabbit cardiomyocytes were loaded with 5 mM 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ), a specific fluorescence indicator that is quenched by Cl− so that cellular efflux of Cl− results in an increase in SPQ fluorescence. [ABSTRACT FROM PUBLISHER]