The effect of 3-aminobenzamide, an inhibitor of poly-ADP-ribose polymerase, on ischemia/reperfusion damage in rat retina.

Excitotoxic amino acids, such as glutamate, may play an important role in retinal ischemia/reperfusion damage. In central neurons, excitotoxicity may be mediated by nitric oxide synthase (NOS) causing DNA damage via nitric oxide (NO). The nicked DNA activates poly-adenosine diphosphate (ADP)-ribose polymerase (PARP) and may deplete intracellular ATP resulting in cell death. PARP may also be involved in apoptosis. We used 3-aminobenzamide (3-ABA), a PARP inhibitor, to examine the possible involvement of PARP in a rat model of retinal ischemia. Retinal ischemia was induced by elevating the intraocular pressure (IOP) through the insertion of a needle into the anterior chamber of a rat eye. IOP was raised to 110 mm Hg for 60 minutes. Animals were given intracameral infusion of 0, 1, 3, 10, 30, 100 mM 3-ABA in 0.1 M PBS, pH 7.4 during ischemia. Morphologic and morphometric evaluation at 7 days after reperfusion showed that 3-ABA at 3 mM and above significantly ameliorated the ischemic/reperfusion damage to the retina. In addition, at 10 mM 3-ABA inhibited the characteristic ladder pattern in DNA gel analysis seen in apoptosis of retinal neurons after ischemia/reperfusion. Hence, PARP may be involved in retinal cell loss after ischemia/reperfusion insult probably through the apoptotic pathway.