Stimulation by Insulin and Glucagon of Ornithine Decarboxylase Activity in Perfused Rat Livers

The effects of insulin and glucagon on ornithine decarboxylase activity were determined in perfused rat livers and compared with the effects of these agents on tyrosine aminotransferase. Insulin stimulated ornithine decarboxylase activity with or without amino acids in the perfusion medium. Glucagon stimulated this enzyme in perfusions with added amino acids, but decreased it in the absence of added amino acids. Tyrosine aminotransferase was increased by both agents with or without added amino acids. The increase in ornithine decarboxylase began in the second or third hour of perfusion, whereas tyrosine aminotransferase increased within 1 hr of hormone addition. (Endocrinology 93: 640, 1973)