The overactivation of the nuclear
enzyme poly(ADP-ribose) polymerase (PARP) is considered a final common effector in
ischemia/reperfusion (I/R) injury. The aim of the current study was to examine the precise time course of the activation of PARP in peripheral leukocytes and the reperfused myocardium tissue on myocardial I/R injury from the same rat and to identify the relationship between
myocardial infarct size and the degree of PARP activation in circulating leukocytes. Another aim of the study was to test the effect of
3-aminobenzamide (a well-known and widely used
PARP inhibitor) on the activation of PARP in the reperfused myocardium and peripheral leukocytes.
Poly(ADP-ribose) polymerase activation was measured by Western blotting for its product,
poly(ADP-ribose) (PAR). The localization of PARP activation was determined by PAR immunohistochemistry. The results showed that poly(ADP-ribosyl)ation was detected 15 min, peaked 2 to 6 h, and remained markedly detectable 24 h in the reperfused heart after I/R model. Similarly, PAR content of the leukocytes increased in cells isolated just after reperfusion from the same rat. Immunohistochemical studies localized the staining of PAR primarily to the cardiac myocytes and vascular endothelial cells. At 6 h, there was a significant linear correlation between
infarct size and PARP activity, whereas at 2 and 24 h, no relationship was found. The
PARP inhibitor 3-aminobenzamide (3-AB, 20 mg kg⁻¹ i.v. injection 15 min before reperfusion, and every 2 h thereafter for 6 h) markedly reduced
infarct size through depressing the activation of the
enzyme in myocytes and peripheral leukocytes even when the treatment is initiated at 2 h after reperfusion.