Regulation of Serine Dehydratase Induction in Rat Liver 1

Summary

When amino acids are infused intravascularly, the enzyme, serine dehydratase, is not induced in liver of adrenalectomized rats as it is when amino acids are given orally. The amino acids appear not to act directly on the liver to induce the enzyme. In fact when injected intravascularly, they inhibit the normal glucagon induction of serine dehydratase but not that induced by hydrocortisone. Intravascular administration of either histidine or concentrated NaCl is inhibitory as are amino acids administered intravascularly to the diabetic rat. The uptake of amino acids and glucose by the liver of glucagon-treated rats after amino acid infusion as measured by distribution of ³H-cycloleucine and ¹⁴C-methyl glucoside is the same as in rats treated with glucagon only. Thus it appears that insulin is not the factor responsible for the inhibition of enzyme induction.

The authors express appreciation to Dr. H. C. Pitot for helpful suggestions and discussion during the course of the experiments and to Suzanne M. Brown and Annabelle Cutler for excellent technical assistance.