Effects of starvation and diabetes on protein synthesis in lung

Metabolism of lung proteins was investigated in rats starved 3 days or made diabetic with streptozotocin. Body weight was below normal in both groups, but lung weight decreased only in starved animals. Total lung protein and RNA (mg/lung) decreased during starvation and diabetes. Protein concentration (mg/g) was unchanged in either group of animals; RNA concentration decreased only during starvation. Protein synthesis, estimated in lungs perfused in situ, was reduced 22% in starvation, but remained unchanged in diabetes. Inhibition of protein synthesis was accounted for by loss of RNA. Ribosomal profiles were unchanged by starvation, suggesting an unaltered relationship between rates of peptide-chain initiation and elongation in vivo. Activity of an eIF-2-like initiation factor decreased during starvation in proportion to the loss of RNA. In diabetes, factor activity remained normal. Thus, starvation but not streptozotocin-induced diabetes, reduced the capacity of the lung to synthesize protein. No evidence for reduced efficiency of synthesis was observed.