Annexin V labels apoptotic neurons following hypoxia-ischemia

THE translocation of phosphatidylserine from the cytosol to the external surface of the plasma membrane has been documented as a characteristic feature of apoptosis in a number of cell types. Annexin V is a calcium-dependent phospholipid binding protein that has high affinity for phosphatidylserine. To investigate whether Annexin V provides a marker of apoptosis in the central nervous system we carried out histochemical analysis of its binding in the 21-day-oId rat brain at various time-points following a moderate unilateral hypoxic-ischemic (HI) insult. The CAI pyramidal neurons, which are selectively vulnerable to HI injury and that die by an apoptotic mechanism showed an increase in Annexin V binding 48-168 hours post-insult.