Hibernation in frogs induces significant morphofunctional adaptations in the myocardium, including reduced contractile tension and altered calcium metabolism.
Hypothesis-generating for myocardial adaptations to metabolic suppression in amphibians; leaves open translation to mammalian or human cardiac protection.
The present study describes morphological and functional changes in the ventricular myocardium of Rana esculenta during hibernation, in comparison with active life. Contractile performance was analyzed in vitro on isolated ventricular trabeculae. Morphological studies were carried out with light and electron microscopy. In hibernating frogs, the myofibrillar apparatus appeared deteriorated and dispersed in an abundant paraplasma mainly consisting of glycogen granules. The accumulation of glycogen was confirmed by the intense staining with the PAS reaction. In accordance with morphological changes, tension development was reduced in trabeculae isolated from hibernating frogs. Whereas force‐velocity relations did not show any difference between trabeculae from hibernating frogs and those from active frogs, significant differences were found in some parameters related to excitation‐contraction coupling. In hibernating frog trabeculae, the relaxation phase was prolonged and the optimal interval of both transient and steady‐state force‐interval relations was lengthened. These changes, which point to a different calcium metabolism in car‐diomyocytes from active and hibernating frogs, were in agreement with the lower activity of the Ca2+‐ATPase observed in hibernating frog myocardium.
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Barni et al. (1994) studied this question.
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