Chloride Channel Inhibition Blocks the Protection of Ischemic Preconditioning and Hypo-Osmotic Stress in Rabbit Ventricular Myocardium

Abstract—The objective of this study was to examine the role of chloride (Cl–) channels in the myocardial protection of ischemic preconditioning (IP). Isolated rabbit ventricular myocytes were preconditioned with 10-minute simulated ischemia (SI) and 20-minute simulated reperfusion (SR) or not preconditioned (control). The myocytes then received 180-minute SI or 45-minute SI/120-minute SR. Indanyloxyacetic acid 94 (IAA-94, 10 μmol/L) or 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, 1 μmol/L) was administered before IP or before SI or SI/SR to inhibit Cl– channels. Electrophysiological studies indicate that these drugs, at the concentrations used, selectively abolished Cl– currents activated under hypo-osmotic conditions (215 versus 290 mOsm). IP significantly (P<0.001) reduced the percentage of dead myocytes after 60-minute (30.8±1.3%, mean±SEM), 90-minute (35.3±1.3%), and 120-minute (39.2±1.7%) SI compared with controls (44.7±1.6%, 54.5±1.3%, and 58.9±1.8%, respectively) and after 45-minute SI/120-m...