Identification of necrotic cell death by the TUNEL assay in the hypoxic-ischemic neonatal rat brain.

The time course and localization of DNA fragmentation in a neonatal rat model of unilateral hypoxia-ischemia were assessed by means of the terminal transferase-mediated biotin dUTP nick end labeling (TUNEL) assay. TUNEL-positive cells were detected in the hemisphere ipsilateral to the ligation immediately after the injury and increased to reach a maximum 1-3 days later, then decreasing until day 10, in parallel with cell death identified by standard histological methods. Cells showing any of the different morphologies of chromatin condensation and fragmentation were labeled, particularly within the core of the ischemic lesion. These results, obtained in a paradigm of necrosis in the immature brain, add to previous evidence suggesting that some forms of non-apoptotic DNA fragmentation are labeled by the TUNEL assay.