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

The temperature-dependence of infraeeliular free caleimn (Ca) was investigated in mdo-1 loaded ventricular myocytes from the ral, a non-hibernator, and from the ground squirrel, a hibernator. The dissociation constant of indo-l at different temperatures was calibrated both al pll-tat and at @-stat . and the result demonstrated that the @-stat ralibration should be prettrred . Analysis of the fluoreseent image showed a striking increase of Ca2 as well as spontaneous caleiuni waves in ral cells, indicating an overloaded cakuum. In contrast, cardiac myocytes of the ground sqnirraf were found to keep a constant (Ca2 ) without caleium overload regardless of temperature variation. It is be-lieved that understanding of the mechanisms underlying the interccllular caleima homeostasis of hibrernators may lead to solutions of some medical questions .