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 ([Ca(2+)](i)) was investigated in indo-1 loaded ventricular myocytes from the rat, a non-hibernator, and from the ground squirrel, a hibernator. The dissociation constant of indo-1 at different temperatures was calibrated both at pH-stat and at alpha-stat, and the result demonstrated that the alpha-stat calibration should be preferred. Analysis of the fluorescent image showed a striking increase of [Ca(2+)](i) as well as spontaneous calcium waves in rat cells, indicating an overloaded calcium. In contrast, cardiac myocytes of the ground squirrel were found to keep a constant [Ca(2+)](i) without calcium overload regardless of temperature variation. It is believed that understanding of the mechanisms underlying the intercellular calcium homeostasis of hibemators may lead to solutions of some medical questions.
College of Life Sciences, Peking University, 100871, Beijing, China.
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Wang
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Zhou
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Qian