BCL-2, BAX AND BCL-X EXPRESSION FOLLOWING HYPOXIA-ISCHEMIA IN THE INFANT RAT-BRAIN

Severe hypoxic-ischemic cerebral damage was produced in 8-day-old rats following permanent bilateral carotid artery occlusion and 15 min of ischemia. Cellular damage consisted of early necrosis and appearance o f cells with apoptotic-like morphology (karyorrhectic cells) and cells with granular chromatin degeneration in the cerebral cortex, hippocam pus, thalamus, striatum and amygdala. Expression of Bcl-2, Fax and Bcl -x was examined in control and hypoxic-ischemic rats using immunohisto chemistry and Western blotting. Members of the Bcl-2 family were expre ssed in the vast majority of, if not all, neurons in control pups. Bcl -2, Bar and Bcl-x immunoreactivity decreased in necrotic cells, but ab out 60% of cells with apoptotic-like morphology and cells with granula r chromatin degeneration were stained with antibodies to Bcl-2, Bar or Bcl-x. Although the total number of stained cells decreased with time , recruitment of cells with apoptotic morphology and cells with granul ar chromatin degeneration was still found up to 48 h. Western blots sh owed a band at about p28 and p21, respectively for Bcl-2 and Bar in co ntrol and hypoxic-ischemic pups at 6, 12 and 24 h. Two bands at about p37 and p30, representing Bcl-xL and Bcl-xS, respectively, were found in samples stained with antibodies to Bcl-x. No gross changes in the i ntensity of these bands were observed in ischemic pups at 6, 12 and 24 h, except for a slight decrease in Bcl-2 at 24 h, and a slight and in constant increase of the putative Bcl-xS at 12 h. These results sugges t that Bcl-2, Fax, Bcl-xL and Bcl-xS do not play a leading role in the fate of damaged nerve cells following a severe hypoxic-ischemic insul t of the developing brain.