[Some features of [1-14C] leucine exchange in rat liver during acute oxythiamine avitaminosis].

The leucine content in rat liver and blood serum under acute oxythiamine avitaminosis is decreased. Simultaneously oxythiamine inhibits the activity of alpha-ketoisocaproate dehydrogenase resulting in a decrease of leucine catabolism in the liver. The level of total tRNA in hepatocyte cytosol is lowered, the radioactivity of leucine in aminoacyl-tRNA on the 6th min after injection of [1-14C]leucine is increased approximately 1.5-fold as compared to normal. The radioactivity of leucine in blood serum and aminoacyl-tRNA is directly significantly correlated with the content of leucine incorporated into the proteins, while the level of intracellular [14C]leucine is not correlated with the protein radioactivity (r=-0.154,p greater than 0.5) or with blood serum amino acid radioactivity (r=-0.184, p greater than 0.5). The results obtained thus indicate that 1) in acute oxythiamine avitaminosis when the labelled amino acid is incorporated within 3-6 min the label is "concentrated" in blood serum resulting in increased specific radioactivity of the protein in rat liver; 2) in blood serum leucine is predominantly utilized during protein biosynthesis; 3) acute oxythiamine avitaminosis has no significant effect on protein biosynthesis in rat liver; 4) specific radioactivity of the protein cannot serve as an index of protein synthesis rate.