Calcitonin increases alanine aminotransferase activity related to calcium in the hepatic mitochondria of rats.

Abstract

The effect of calcitonin (CT) on alanine aminotransferase activity and calcium content in the hepatic mitochondria of intact rats was investigated. A single subcutaneous administration of CT (synthetic [Asu1,7] eel calcitonin; 80 MRC mU/100 g body weight) produced a significant increase in alanine aminotransferase activity and a corresponding elevation of calcium content. Those increases were also observed with the lowest dose of CT (20 MRC mU/100 g). The mitochondrial calcium depletion by 10 mM EGTA treatment produced a remarkable reduction in alanine aminotransferase activity increased by CT, although EGTA treatment did not alter basal enzyme activity. Addition of calcium ion (1-10(3) microM) into the EGTA-treated mitochondria, however, produced a significant increase in alanine aminotransferase activity. The enzyme activity increased by CT was not inhibited by the presence of calmodulin inhibitor, W-7 (1-10(3) microM). These results suggest that the mitochondrial calcium increased by CT administration directly activates alanine aminotransferase in the hepatic mitochondria of rats.