Effect of whole-body X-irradiation on rat liver protein synthesis at translational level

Whole-body exposure of rats to X-rays resulted in the elevation of monosome-polysome populations in nuclear, post-nuclear and post-mitochondrial fractions of liver. Irradiation exerted no influence on the ratio of free to membrane-bound polysomes but shifted the profiles towards the heavier polysomes. At 18 hr post-irradiation, the rate of nascent polypeptide formation, as assessed by giving a 5 min pulse of (14C) leucine intraperitoneally, was enhanced on the free polysomes but not on the membrane-bound polysomes. Further, ribosomes derived from free polysomes were much more efficient than membrane-bound polysomes in incorporating (14C) phenylalanine into polypeptides in poly U-directed in vitro system after whole-body radiation exposure. (author)