The effects of food deprivation on in vivo gluconeogenesis in the suckling rat.

Abstract

Thyroidectomized rats inj~-cted daily with 0, 0.1, 2 or 251'1! of L•lhyroxineilOOg body wt. were compared with intact controls. [n plasma, the protein-bound iodine was decreased in the rats given the O or 0.1 ,,g do~s and increased in those given the 2Sµg do~e. 2. Blood glucose Jc~rea,ed in those ~iven 21111, a11J was augmtn1~d in those given 2514g, and ketone bodies were the sam, in all the groups. 3. Plasn.a in~ulin was lowest in the rats given the O or 0.1 µg doses and was highe,t in those given the 2 or 25;,a do!cs of thyroxine. 4. After 48h stal"\·ation, the decrea~ in blood gh,cos, and increase in ketone bodies observed in oil the groups was grearest in the group not suprlemerited with thyro,i;inc. 5. Plasma insulin concentrations remained at the value for fed animals in the rats given the 25µg dose of thyroxine but decreased in the other groups. 6. In fed animals, concentrations of hepatic DNA P, citrate, total farty acids and ace1yl-CoA were similar in all the groups, and glyc()gen "as low only in the rats given the 2Srg dose of thyroxine. 7. After 48h starvation, liver DNA P, total fatty acids and acetyl-CoA increased in all the j1!roups, except in the rats given the 25rg dose, where both total fatty acids and acctyl-CoA remained al the value for fed animals. Liver citrate did not change in the groups given lhe O or 251•& doses of thyroxine, but decreased in the other groups. 8. The results arc discussed in relalion to the regulation of intermediary metabolism in hypo- and hyper-thyroidism.