AJP - Heart and Circulatory Physiology, Vol 261, Issue 5 1609-H1616, Copyright © 1991 by American Physiological Society
Calcium and cardioplegia in neonates: dose-response and time-response studies in rats
E. Riva and D. J. Hearse
Cardiovascular Research, Rayne Institute, St. Thomas' Hospital, London, United Kingdom.
Isolated Langendorff-perfused rat hearts (n = 6/group) were subjected to
60, 90, 120, or 180 min of ischemia with or without a 2-min preischemic
infusion with St. Thomas' Hospital cardioplegic solution that had been
modified to contain concentrations of calcium of 0, 0.5, 0.8, 1.0, 1.2,
1.8, or 2.4 mM. In general, irrespective of the calcium concentration,
hearts in the cardioplegia group recovered better than those in the
noncardioplegia group. There was no consistent relationship between calcium
content and postischemic recovery of function or enzyme leakage after any
of the durations of ischemia studied. However, as expected, there was a
strong inverse relationship between recovery and duration of ischemia. The
recovery of function correlated with enzyme leakage but not with the time
to onset or magnitude of ischemic contracture. In conclusion, although the
neonatal rat heart benefits from cardioplegia the protection is less
impressive than that reported for adult hearts. Nonetheless, the neonatal
heart appears to be very resistant to ischemia. We propose that many of
these differences can be explained on the basis of differences in
myocardial calcium handling between neonate and adult.
