AJP - Heart and Circulatory Physiology, Vol 253, Issue 6 1358-H1364, Copyright © 1987 by American Physiological Society
Quantification of calcium paradox in neonatal rat hearts
J. S. Elz and W. G. Nayler
Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
Many indexes of damage have been used to quantify the calcium (Ca2+)
paradox. We report here how different conclusions may be reached concerning
the severity of the paradox when different indexes of damage are used.
Hearts from 3- to 24-day-old and adult rats were isolated, depleted of Ca2+
for 5 min, and then Ca2+ repleted. Myoglobin loss, Ca2+ gain, and
ultrastructural changes were monitored. Our results indicate that with
increasing age each of these parameters shows a progression toward the
adult state. However, this progression does not proceed at the same rate
for each parameter. There was very little release of myoglobin from hearts
of rats of less than 11 days old, but the amount released increased with
increasing age. There appeared to be a direct relationship between the
amount of myoglobin released and the proportion of extremely contracted
cells with disrupted sarcolemma. However, hearts from rats of all ages
gained Ca2+, suggesting that Ca2+ entry occurs via contracture-dependent
and contracture-independent routes. Thus we are able to dissociate Ca2+
gain from the development of contracted cells and myoglobin release at the
youngest ages. Different conclusions could therefore be reached as to the
severity of the Ca2+ paradox at these youngest ages depending on which
indexes of damage are documented.
