Comparative studies of intra- and extramitochondrial calcium phosphates from the hepatopancreas of the blue crab (Callinectes sapidus).

Subcellular fractions of cytoplasmic mineral granules and mineral-loaded mitochondria were isolated from whole homogenates of hepatopancreas of the blue crab (Callinectes sapidus). Chemical, physical, and morphologic studies were carried out on both subcellular fractions, with and without prior removal of organic components by hydrazine extraction. In contrast to cytoplasmic granules, whole mitochondria contained appreciable amounts of mineral ions not associated with a solid mineral phase. Quantitative analyses and infrared spectroscopy showed cytoplasmic and mitochondrial mineral phases to be calcium phosphates of similar but not identical composition. Both cytoplasmic and mitochondrial mineral phases, as in synthetic amorphous calcium phosphate, show noncrystalline patterns when examined by infrared spectroscopy and x-ray diffraction, and a common ultrastructure of clustered spheres of approximately 100 A diameter. The findings suggest that amorphous calcium phosphate in biological systems may exhibit appreciable variation in Ca/P and in the content of foreign ions such as Mg2+, ADP, and ATP. A mitochondriogenic mechanism of calcification could not be confirmed nor refuted by this study.