Fate of elevated L-tryptophan in the blood of nephrotic rats with oral L-tryptophan administration in their body.

We examined the changes in serum, liver, kidney, brain, and muscle L-tryptophan (Trp) levels in rats with puromycin aminonucleoside (PAN) nephrosis following oral Trp administration in order to elucidate the fate of elevated Trp in the blood of PAN nephrotic rats with oral Trp administration in their body. Before administration, nephrotic rats had higher liver and kidney Trp contents and lower serum Trp concentration than non-nephrotic rats. At 15 min after oral administration of Trp (100 micromol/kg body weight), PAN nephrotic rats had a much higher amount of liver Trp than non-nephrotic rats but there were no differences in increased amounts of serum, kidney, brain, and muscle Trp between the two groups. At 30 min after oral Trp administration, PAN nephrotic rats had a lower increased amount of serum Trp than non-nephrotic rats and had no increase in liver Trp content, although the increased amounts of Trp in other tissues were similar in both groups. At 30 min after oral Trp administration, liver tryptophan 2,3-dioxygenase activity increased approximately 2 fold in PAN nephrotic rats. These results indicate that elevated Trp in the blood of PAN nephrotic rats with oral Trp administration is transported mainly into the liver rapidly and then the transported Trp is actively metabolized by activated tryptophan 2,3-dioxygenase in the tissue.