The changes of hepatic lysosomal cathepsins, alanine aminotransferase (AAT) activities and serum amino acids were studied on rat fed on high and low protein diets with or without B_6. The group fed on high protein diet without B_6 caused the marked suppression of growth and also in the pathological bad lie of hair with dermatosis, while these pathological syndromes were not observed in rats fed on low protein diet without B_6. The activities of cathepsins B, L, H and J in rats fed on high protein diet these cathepsin activities were not affected by B_6 deficiency. Therefore, the biosynthesis and also degradation of these cathepsins are not influenced by B_6 deficiency. Some amino acid levels in serum were increased by high protein diet intake and B_6 deficiency. The levels of glycine were significantly decreased in rat fed on high protein diet. The levels of aspartate and glycine were markedly elevated in the cases of B_6 deficiency and those of alanine and hydroxyproline were decreased in the cases of B_6 deficiency.
