Effects of insulin on amino acid and ribonucleic acid metabolism in rat adipose tissue.

Trichloroacetic acid precipitable protein and ribonucleic acid were isolated from paired pools of rat epididymal fat pads after in vitro incubation. Insulin in vitro, without glucose, had no effect on the incorporation of carbon from uniformly labeled glycine-C 14 , l-proline-C 14 or l-histidine-C 14 into adipose tissue protein. In the presence of as little as 0.1 µm/ml of unlabeled glucose, insulin markedly increased the incorporation of carbon from these three amino acids into protein. Insulin in vitro also increased the incorporation of carbon from glucose-U-C 14 into both ribonucleic acid and protein. The recovery of C 14 derived from glucose-6-C 14 in the ribonucleic acid of adipose tissue relative to that from glucose-1-C 14 was increased when insulin was present. Insulin increased the incorporation of C 14 from pyruvate-2-C 14 into adipose tissue protein in the absence of added glucose. The addition of glucose had no effect on the recovery of C 14 from pyruvate-2-C 14 when insulin was present. Carbon-14 from pyruvate-2-C 14 was incorporated into ribonucleic acid, but insulin did not increase its incorporation.