Calcitonin increases pyruvate carboxylase activity in hepatic mitochondria of rats.

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Abstract
The effect of calcitonin (CT) on Ca content and enzyme activity in the hepatic mitochondria of intact rats was investigated. A single s.c. administration of CT (80 MRC [Medical Research Council] mU/100 g BW [body wt]) produced a significant increase in the content of Ca, the activity of pyruvate carboxylase, succinate dehydrogenase and ATPase 15 min after the hormone tratment. The significant increases in Ca content and pyruvate carboxylase activity were also observed 30 min after CT administration, while succinate dehydrogenase and ATPase activity began to decrease. A physiological dose of CT (20 MRC mU/100 g BW) caused a marked increase in Ca content and pyruvate carboxylase activity but not succinate dehydrogenase or ATPase-activity. The removal of Ca by 10 mM ethylene glycol-bis(.beta.-aminoethyl ether)N,N,N'',N''-tetraacetic acid washing of the mitochondria produced a remarkable reduction in pyruvate carboxylase activity increased by CT administration. The addition of Ca ion of 2.5 .times. 10-2-2.5 .times. 101 nmol Ca2+/mg mitochondrial protein produced a marked increase in pyruvate carboxylase activity. Ca taken up by the hepatic mitochondria after CT administration apparently activates pyruvate carboxylase.