Temperature dependence of intracellular free calcium in cardiac myocytes from rat and ground squirrel measured by confocal microscopy

The temperature-dependence of intracellular free calcium ([Ca2+](i)) was in vestigated in indo-1 loaded ventricular myocytes from the rat, a non-hibern ator, and from the ground squirrel, a hibernator. The dissociation con sten t of indo-1 at different temperatures was calibrated both at pH-stat and at a-stat, and the result demonstrated that the a-stat calibration should be preferred. Analysis of the fluorescent image showed a striking increase of [Ca2+](i) as well as spontaneous calcium waves in rat cells, indicating an overloaded calcium. In contrast, cardiac myocytes of the ground squirrel we re found to keep a constant [Ca2+](i) without calcium overload regardless o f temperature variation. It is believed that understanding of the mechanism s underlying the intercellular calcium homeostasis of hibernators may lead to solutions of some medical questions.