Possible role of PARP activation in testis. Under physiological conditions, mild DNA damage is repaired by PARP activation. Pathological conditions, associated with more severe oxidative stress, may cause excessive PARP activation and result in apoptotic cell death. Under physiological conditions, blockage of PARP activity with PARP inhibitors may inhibit DNA repair and lead to apoptotic cell death. On the other hand, the inhibition of extensive activation of PARP in pathological conditions may prevent apoptotic cell death.