The intracellular distribution of liver cell calcium in normal rats and one hour after administration of carbon tetrachloride.

In order to recognize the significance of elevated liver calcium level in the early phase of carbon tetrachloride intoxication, the subcellular distribution of calcium in liver was investigated one hour after administration of CCl4 intraperitoneally. During preparation of subcellular fractions attempts were made to prevent redistribution of calcium by adding Ruthenium Red and EGTA or LaCl3 to homogenization medium, and by shortening of differential centrifugation to a minimum. The latter caused a loss of purity in sub cellular fractions which was overcome by correction of calcium values from atom absorption spectrometry by means of marker enzyme activity. The calcium levels in normal rat liver were found to be 70 nmoles/g liver wet wt in cytosol, 310 nmoles/g liver in microsomes and about 500 nmoles/g liver in mitochondria. A minor part of the latter fraction may belong to nuclei and plasma membranes. One hour after CCl4 administration calcium levels in cytoplasma were not altered, in microsomes were decreased to 200 nmoles/g liver and in mitochondria were elevated to 2.5 mumoles/g liver. In rats pretreated with vitamin D the whole additional calcium, after carbon tetrachloride application in the range of 9 mumoles/g liver, was sequestrated in mitochondria. In the early phase of carbon tetrachloride intoxication all border membranes of liver cells have to participate in bringing about the reversible increase of liver cell calcium.