Synthetic [Asu1,7] eel calcitonin increases phosphorus content in the hepatic mitochondria of rats

The change of subcellular phosphorus content in the liver was investigated after a single sc administration of synthetic [Asu1,7] eel calcitonin (CT) to fed rats. Administration of CT (80 MRC mU/100 g body weight) produced a significant increase in phosphorus content in the mitochondrial fraction, while this increase was not observed in fractions containing plasma membrane, nuclei, microsomes and cytosol. A significant increase in the mitochondrial phosphorus content was observed even at the lowest dose of CT (40 MRC mU/100 g body weight). A single ip administration of 2,4-dinitrophenol (0.1 mg/100 g body weight), an inhibitor of oxidative phosphorylation, did not prevent significant increases in phosphorus contents of the homogenate and the mitochondria caused by administration of CT (80 MRC mU/100 g body weight), although the drug markedly inhibited ATPase activity in the mitochondria. Administration of CT did not produce a significant alteration in the mictochondrial ATPase activity. These results suggest that phosphorus taken up by the liver cells after CT administration is largely located in the mitochondria, and that this increase is not related to oxidative phosphorylation. Presumably the hepatic mitochondria play a role in the storage of intracellular phosphorus increased by CT.