Analysis of ion distribution in subcellular myocardial particulates separated by density gradient centrifugation with nonpolar liquid under ion immobilization conditions.

Methods have been developed for the measurement of the Ca and Mg contents of subcellular particulates, separated by nonpolar liquid density gradient ultracentrifugation. After rapid deep freezing and removal of water by freeze-drying the frozen crushed tissue, homogenization and sonification a nonpolar liquid were carried out. Application of this technique has yielded evidence that the relative amounts of Mg and Ca are greatly different in the several subcellular particulates of normal heart muscle separated by density gradient centrifugation. It also appears that the comparative specific activity of Ca, after loading the perfusates with 45Ca, is very different in the several density fractions of the normal heart. The density site of greatest loading with 45Ca is changed in Ca2+-lack arrest and is very greatly altered by the induction of paradoxical Ca contracture. The method of ion-immobilization separation for water-free particulates of different densities in nonpolar liquids appears to be applicable to analysis for various constituents of other biological materials.