Although the mean ornithine decarboxylase (ODC) activity induced by feeding in alloxan-diabetic rats was 60% of that in normal rats, it was markedly suppressed in pancreatectomized rats depending on the degree of pancreatectomy. 2. There was a correlation between plasma glucagon concentration and hepatic ODC activity under various dietary conditions. 3. When glucagon or insulin was given to pancreatectomized rats, dietary induction of ODC was restored to a level found in normal rats. The effects of glucagon and insulin were not additive, suggesting that these hormones act with a similar mechanism. Feeding 75% casein diet resulted in a considerable induction of ODC even in pancreatectomized rats. The enzyme was only slightly induced, however, when pancreatic hormones were given to starved rats. 4. Findings from amino acid analysis indicated that the influx of some amino acids into liver was stimulated by administration of glucagon. 5. These results suggest that increased influx of amino acids into liver is a critical factor for dietary induction of ODC and that both glucagon and insulin play a role in stimulating amino acid influx.
