The hamster heart is resistant to calcium paradox

Reintroduction of Ca2+ or modification of internal Ca2+ stores by caffeine results in widespread irreversible injury. The adult golden hamster, howeve r, is immune to such insult and the present report investigates the phenome non. Isolated Langendorff perfused hamster and rat heart were subjected to 15 min Ca2+-free perfusion followed by 30 min of Ca2+ perfusion at 37 degre es C. Caffeine was introduced during Ca2+-free perfusion in a number of exp eriments. Papillary muscles were processed for the ultra-structural study. The hamster heart did not exhibit the calcium parader; state whereas rat he art did. Hamster heart treated with caffeine either throughout or 5 min aft er starting Ca2+-free perfusion showed 70% +/- 8 or 65% +/- 8.42 recovery, respectively, when Ca2+ reperfusion was performed. Ultrastructure of muscle from both groups showed relaxed myocytes with slight disorientation of the sarcomere register. This disorientation was not seen in hamster hearts und ergoing the conventional calcium paradox protocol. The hamster cardiac musc le is remarkably tolerant to [Ca2+](i) loading either induced by Ca2+ reper fusion or caffeine-induced sarcoplasmic reticulum Ca2+ release. Structural and functional characterization of Ca2+ depletion and repletion in the hams ter heart have been discussed. (C) 2000 Academic Press.