Calcium paradox in guinea‐pig ventricular myocytes

Abstract

SUMMARYMeasurement of the release of lactate dehydrogenase (LDH), the development of contracture and the exclusion of the dye Trypan Blue were made in isolated guinea-pig ventricular myocytes subjected to conditions that evoke a calcium paradox in intact heart. Incubation at 25°C reduced the release of LDH associated with mechanical manipulation of the myocytes so that during prolonged incubation in media free of Ca2' and Mg2+ ions at 25°C little release of LDH occurred.A significant release of LDH into the incubation media was provoked on repletion of the divalent cations. This release was accompanied by a marked decrease in the percentage of rod-shaped myocytes and their ability to exclude Trypan Blue. The results provide evidence for the existence of the calcium paradox in isolated guinea-pig ventricular myocytes as originally defined.

MAPK activation and apoptotic alterations in hearts subjected to calcium paradox are attenuated by taurine

“…Although Piper et al [42] have shown that that Ca 2+ -paradox does not occur in cardiomyocytes unlike isolated heart, others have established the existence of Ca 2+ -paradox in cardiomyoctes [43]. The occurrence of Ca 2+ -paradox in the present study was evident from the observation that a significant reduction in the number of rod shape cardiomyocytes and their ability to exclude trypan blue after Ca 2+ -repletion was observed in accordance with the previous studies [44]. While, the potential importance of cell death due to apoptosis by increase in [Ca 2+ ] i is not fully understood, an increase in [Ca 2+ ] i as a stimulus for apoptotic cell death has been demonstrated in lymphoid cells, leukemic T-cells and cytotoxic T-cells [7].…”