[Protein metabolism in vitamin A deficient rats. I. Protein and DNA turn-over in rat liver]

The effect of a vitamin A deficient diet on liver proteosynthesis was studied with in vivo and in vitro methods. Weanling rats obtained from vitamin A rstricted female were fed "separate diet". Control animals received vitamin A in protein diet. Deficient rats were used at the weight plateau stage. The RNA, DNA and protein liver content was unaffected by vitamin A deficiency and the same result was found for free amino acid pool. The turn-over rate of protein and RNA of cellular fractions and total liver was studied. (14C) leucine and (3H) uridine was injected intraperitoneally. Animals were killed at 20-40 minutes and 2-4-6-8-10 days after injection. Synthesis rate of liver proteins was the same in both groups. Our results indicate no difference in the average rate of (14C) protein degradation between control and deficient animals. Vitamin A deficiency decrease the turn-over rate of total ribosomal and soluble RNA. Polyribosome and postribosomal supernatant from deficient rats liver were less active for protein synthesis in vitro than corresponding fractions from well nourished rats. The lesion was located in the post ribosomal supernatant fraction by "crossing over" experiments. Polyribosome desimentation analysis on sucrose gradients revealed no difference between the two groupe. The results indicate that vitamin A deficiency decrease cell proliferation without degeneracy. The limitative agent of proteosynthesis is situated at RNA level. However protein synthesis is unaffected in our experimental procedure.