Effects of protein-deprivation on the regeneration of rat liver after partial hepatectomy.

Rats maintained on a protein-free diet for 3 days have an altered time course of hepatic DNA synthesis during liver regeneration. The delay in DNA synthesis is eliminated by the administration of casein hydrolysate (given as late as 6h after partial hepatectomy), but not by glucose or incomplete amino acid mixtures. Despite the change in the timing of DNA synthesis, the increases in hepatic amino acid pools, which take place at the earliest stages of the regenerative process, occur in a normal pattern in the regenerating liver of rats fed the protein-free diet. Protein-deprived rats have increased protein synthesis and decreased rates of protein degradation in the liver in response to partial hepatectomy, but these adaptations do not prevent a lag in protein accumulation and low protein/RNA ratios. The regenerating livers of these animals show a deficit in the accumulation of cytoplasmic polyadenylated mRNA as well as a smaller proportion of free polyribosomes. It is suggested that the deficit in free polyribosomes found in the regenerating liver of protein-deprived rats might be a consequence of the slow accumulation of mRNA species coding for intracellular proteins.