Effect of dietary lysine on polyamine synthesis in the chick

Experiments were conducted to determine the effect of dietary lysine on hepatic and renal polyamine synthesis in the chick. High arginine-requiring (HA) and low arginine-requiring (LA) strains were used, with differences in arginine requirements being due, in part, to differences in renal arginase activity. Arginine requirements were 1.2 and 0.9% for the HA strain and LA strain, respectively. A total of 96 chicks (16 per diet, 48 per strain) were fed a crystalline amino acid diet containing requirement concentrations of arginine and 0.95, 1.40 or 1.85% lysine for 2 wk. Hepatic arginase activity was unaffected by dietary lysine in both strains, whereas hepatic ornithine decarboxylase (ODC) activity fell with increased dietary lysine in the LA strain only. Increasing dietary lysine significantly increased renal arginase activity but reduced renal ODC activity in the HA strain only. Increasing dietary lysine also caused decreased renal concentrations of arginine, whereas lysine and ornithine concentration increased in both strains. Concentrations of putrescine also rose. It was concluded that excess dietary lysine increased renal concentrations of ornithine due to induction of arginase. This accumulation of polyamine precursors resulted in increased concentrations of putrescine despite feedback inhibition of ODC.