Possible contribution of a decrease in serum albumin concentration to a low level of blood L-tryptophan in nephrotic rats

In order to clarify whether or not a decrease in serum albumin concentration contributes to a low level of blood L-tryptophan (Trp) in nephrosis, blood Trp concentration at 30, 60, 90, and 120 min after oral administration of Trp (100 mu mol/kg body weight) in the same rats injected once with puromycin aminonucleoside (PAN) (100 mg/kg body weight, i.p.), an inducer of nephrosis, was examined at different stages of nephrosis. The increase and decrease in blood Trp concentration after Trp administration were similar in the PAN-treated rats without nephrosis, the PAN-treated rats recovered from nephrosis, and untreated control rats. The maximum increase in blood Trp concentration at 30 min after Trp administration was lower in nephrotic rats than in control rats. In all rats treated with and without PAN, increased blood L-tryptophan concentrations at 30 min after L-tryptophan administration were positively correlated well with serum albumin concentrations (r = 0.88, p < 0.001). There was no difference in the intestinal absorption of the same dose of orally administered Trp between nephrotic and control rats. These results suggest that a decrease in serum albumin concentration may contribute to a low level of blood L-tryptophan in nephrosis.