A possible block in the intermediary metabolism of glucose into proteins and lipids in the brains of undernourished rats

[U‐ 14 C] Glucose or [1‐ 14 C] L‐leucine was injected intraperitoneally into 28‐day‐old undernourished rats and control sibs who were killed 6 hr later. Brain proteins and lipids were extracted and the lipids fractionated by silicic acid column chromatography into cholesterol, glycolipids and phospholipids. The specific activity of labeled carbon derived from [U‐ 14 C] glucose in brain proteins was reduced by 25% in undernourished animals when compared to controls. A similar reduction was seen in the specific activity of brain lipids of undernourished animals: 14% for cholesterol, 21% for phospholipids and 35% for glycolipids. When [1‐ 14 C] l‐leucine was used as a direct precursor of brain protein synthesis, the specific activity in the undernourished group was only 5% less than that found for the controls. This was not statistically significant. The results suggest that there may be a block in the intermediary metabolism of glucose in the brains of undernourished rats that reduces the availability of glucose carbon to the precursor pool used for protein and lipid synthesis.