BCL-2 AND BAX EXPRESSION IN ADULT-RAT HEARTS AFTER CORONARY-OCCLUSION- AGE-ASSOCIATED DIFFERENCES

It has been reported that programmed cell death (apoptosis) occurs dur ing myocardial infarction. The influence of age on programmed cell dea th or DNA fragmentation after coronary occlusion has not been extensiv ely characterized. To test the hypothesis that there are age-related d ifferences in susceptibility to DNA fragmentation during ischemia-infa rction, we studied DNA fragmentation in young adult and old male F344 rat hearts after acute coronary artery occlusion. Hearts were studied at 1, 3, and 5 h and 1 and 7 days after coronary ligation. The percent age of apoptotic cells was determined by the in situ end-labeling tech nique, and internucleosomal fragmentation (DNAladdering) pattern was a lso analyzed. Our results show that 1) DNA fragmentation began earlier and peaked earlier in the old compared with young adult hearts during infarction; 2) there was heightened expression of both Bcl-2 and Bar in the old hearts at baseline; and 3) the Bcl-2-to-Bax ratio was highe r in the older heart after coronary ligation. These results suggest th at, compared with the young adult heart, the aged heart may be more su sceptible to ischemia-induced DNA fragmentation.