AGE-DEPENDENT CHANGES IN MYOCARDIAL SUSCEPTIBILITY TO ISCHEMIC-INJURY

We studied the relation between age and the heart's ability to tolerat e ischemia. Groups of 5-7 isolated Langendorff perfused hearts from ne onatal (5 days old), immature (11-44 days old), and adult (54 days old ) rats, were subjected to 60 minutes of global ischemia and 60 minutes of reperfusion at 37-degrees-C Pre-ischemic left ventricular develope d pressure was 54 +/- 1, 56 +/- 2, 59 +/- 4, 80 +/- 3, 91 +/- 9, 91 +/ - 8, 94 +/- 3, 101 +/- 10, 107 +/- 8 and 132 +/- 4 mmHg in the 5, 11, 14, 18, 23, 26, 33, 40, 44, and 54 day old groups, respectively. Left ventricular developed pressure recovered to 65 +/- 13, 69 +/- 4, 103 /- 14, 84 +/- 10, 81 +/- 3, 59 +/- 11, 42 +/- 10, 34 +/- 6, 34 +/- 6 a nd 25 +/- 7% respectively. Ischemia-induced contracture was greater in adult hearts and the time-to-onset and the time-to-peak contracture d ecreased with increasing age. Leakage of creatine kinase after ischemi a correlated poorly with the recovery of contraction. Left ventricular end-diastolic pressure, at the end of 60 minutes of reperfusion, incr eased in an age-dependent manner from a pre-ischemic value which was s et at 2-8 mmHg to 14 +/- 4, 22 +/- 2, 21 +/- 5, 2 7 +/- 3, 47 +/- 16, 52 +/- 7, 71 +/- 7, 81 +/- 9, 73 +/- 5, and 82 +/- 8 mmHg in the 5, 11 , 14, 18, 23, 26, 33, 40, 44, and 54 day old groups, respectively. In conclusion, in this study in rats, age-dependent changes in resistance to ischemia presented a biphasic pattern with increasing tolerance up to 23 days of age, followed by a decline. Thus, the immature rat hear t is less susceptible to injury during ischemia and reperfusion than t he neonatal heart and the mature heart is more vulnerable to injury th an the younger heart.