Total aminoacyl-transfer RNA pool is greater in liver than muscle in rabbits

Transfer RNA (tRNA)-charged amino acids are direct precursors of protein synthesis. Therefore, the amount and profile of amino acids in the aminoacyl-tRNA pool may be closely related to the rate of protein synthesis in the tissue. This study was designed to compare the aminoacyl-tRNA pools in liver and muscle, 2 distinct tissues with different rates of protein synthesis. Liver and muscle samples were taken from 6 rabbits and aminoacyl-tRNA was isolated with sequential acidphenol: chloroform extraction, followed by total RNA and tRNA purification. Amino acids in the aminoacyl-tRNA pool were measured by HPLC after deacylation. Liver contained 3.4 times more tRNA than muscle (585 ± 120 vs. 132 ± 11 μg of tRNA/g of tissue; P < 0.001). Overall tRNA charging was also greater in liver (14.22 ± 4.42 nmol of amino acids/mg of tRNA) than in muscle (7.00 ± 1.76 nmol of amino acids/mg of tRNA) (P < 0.05). The greater availability and charging efficiency of tRNA in liver as compared with muscle may influence the extent to which amino acid precursor availability regulates protein synthesis in these 2 tissues.