Until now, most studies carried out on cellular calcium have concerned primarily the free, ionized fraction present in the cytosol, while little is known about the distribution of total calcium (free plus bound). Since in samples fixed conventionally, with or without calcium précipitants, extensive loss and redistribution of cellular calcium from the original sites does inevitably take place, we have developed a procedure for tissue preparation that combines physical and chemical treatments. PC 12 cells (a rat pheochromocytoma cell line) were processed according to this approach and ultrathin sections examined by electron energy loss microanalysis, in the spectrum (EELS) or image (ESI) mode. The highest levels of total calcium were observed in areas of the ER where cisternae are organized in stacks; perinuclear cisternae; Golgi apparatus; secretory vesicles and granules. Parallel immunolocalization experiments, carried out with antibodies specific for various markers such as calreticulin, InsP3 receptors, mannosidase II, and chromogranines, confirmed the identification of the above organelles. The possible significance of very high calcium in specific compartments will be discussed.
|Journal||Biochemical Society Transactions|
|Publication status||Published - 1996|
ASJC Scopus subject areas