Rj. Diaz et al., Chloride channel inhibition blocks the protection of ischemic preconditioning and hypo-osmotic stress in rabbit ventricular myocardium, CIRCUL RES, 84(7), 1999, pp. 763-775
The objective of this study was to examine the role of chloride (Cl-) chann
els in the myocardial protection of ischemic preconditioning (IP). Isolated
rabbit ventricular myocytes were preconditioned with 10-minute simulated i
schemia (SI) and 20-minute simulated reperfusion (SR) or not preconditioned
(control), The myocytes then received 180-minute SI or 45-minute SI/120-mi
nute SR. Indanyloxyacetic acid 94 (IAA-94, 10 mu mol/L) or 5-nitro-2-(3-phe
nylpropylamino)benzoic acid (NPPB, 1 mu mol/L) was administered before IP o
r before SI or SI/SR to inhibit Cl- channels. Electrophysiological studies
indicate that these drugs, at the concentrations used, selectively abolishe
d 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-minu
te (39.2+/-1.7%) SI compared with controls (44.7+/-1.6%, 54.5+/-1.3%, and 5
8.9+/-1.8%, respectively) and after 45-minute SI/120-minute SR (36.3t0.6%)
compared with control (56.6+/-2.2%). Hypo-osmotic stress also produced prot
ection similar to IF. IAA-94 or NPPB abolished the protection of both IP an
d hypo-osmotic stress. In buffer-perfused rabbit hearts preconditioned with
three 5-minute ischemia/10-minute reperfusion cycles given before the 40-m
inute long ischemia and 60-minute reperfusion, IP significantly (P<0.0001)
reduced infarct size (IP+vehicle, 4.7+/-0.9%, versus control+vehicle, 26.6/-3.3%; mean+/-SEM). Again, IAA-94 or NPPB abolished the protection of IF.
Our results implicate Cl- channels in the IP protection of the myocardium a
gainst ischemic/reperfusion injury and demonstrate that hypo-osmotic stress
is capable of preconditioning cardiomyocytes.