Effects of L-lysine administration on certain aspects of ascorbic acid metabolism.

The effects of administration of L-lysine on total ascorbic acid level of various tissues and plasma of rats were studied. The biosynthesis of L-ascorbic acid by the liver tissue was also followed. L-lysine was administered at a dose of 88.3 mg day-1 (20% of LD50) for each 100 g body weight for 14 days. L-lysine administration at the present dose elevated the total ascorbic acid level of liver, kidney, testes, spleen and brain tissues. The plasma total ascorbic acid level was also elevated. The synthesis of L-ascorbic acid from both D-glucuronolactone and L-gulonolactone by the liver was, however, reduced after L-lysine administration. It has been suggested that L-lysine administration at the present dose altered the plasma amino acid pattern which in turn impaired the in vivo synthesis of tissue proteins and, consequently, the synthesis of apoproteins of ascorbic acid-synthesizing enzymes, the D-glucuronoreductase and L-gulonooxidase, were reduced. The elevation in the total ascorbic acid level of extra-hepatic tissues and plasma after L-lysine administration was ascribed to the reduced catabolism and diminished urinary excretion of ascorbic acid.