Inhibition of the Na(+)/H(+) exchanger confers greater cardioprotection against 90 minutes of myocardial ischemia than ischemic preconditioning in dogs.

Gumina RJ, Buerger E, Eickmeier C, Moore J, Daemmgen J, Gross GJ
Circulation. 1999 100 (25): 2519-26; discussion 2469-72

PMID: 10604890 · DOI:10.1161/01.cir.100.25.2519

BACKGROUND - This study compared the efficacy of ischemic preconditioning (IPC) and sodium-hydrogen exchanger (NHE)-1 inhibition to reduce infarct size (IS) induced by a 90-minute ischemic insult and examined the interaction between NHE-1 inhibition and IPC.

METHODS AND RESULTS - In a canine infarct model, either IPC, produced by 1 or four 5-minute coronary artery occlusions, or the specific NHE-1 inhibitor BIIB 513, 0.75 or 3.0 mg/kg, was administered 15 minutes before either a 60- or 90-minute coronary artery occlusion followed by 3 hours of reperfusion. IS was determined by TTC staining and expressed as a percentage of the area at risk (IS/AAR). Although both IPC and BIIB 513 at 0.75 mg/kg produced comparable and significant reductions in IS/AAR in the 60-minute occlusion model, insignificant reductions in IS/AAR were observed in the 90-minute occlusion model. However, BIIB 513 at 3.0 mg/kg markedly reduced IS in both models (P<0.05). Next, to examine the interaction between NHE-1 blockade and IPC, BIIB 0.75 mg/kg was administered either before IPC or during the washout phase of IPC before 90 minutes of coronary artery occlusion. Both combinations resulted in a greater-than-additive reduction in IS/AAR (P<0.05).

CONCLUSIONS - These data demonstrate that although IPC and NHE-1 inhibition provide comparable protection against 60 minutes of myocardial ischemia, NHE-1 inhibition is more efficacious than IPC at protecting against a 90-minute ischemic insult. Furthermore, the combination of NHE-1 inhibition and IPC produces a greater-than-additive reduction in IS/AAR, suggesting either that NHE activity limits the efficacy of IPC or that different mechanisms are involved in the cardioprotective effect of IPC and NHE-1 inhibition.

MeSH Terms (16)

Amiloride Animals Dogs Drug Evaluation, Preclinical Guanidines Hemodynamics Hydrogen Ion Transport Ischemic Preconditioning, Myocardial Mesylates Muscle Proteins Myocardial Infarction Myocardial Reperfusion Injury Sodium Sodium-Hydrogen Exchangers Sulfones

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