Change of serum L-tryptophan levels following the development and recovery of acute puromycin aminonucleoside nephrosis in rats

Summary It is known that total L-tryptophan (Trp) levels decrease with a decrease in albumin-bound Trp levels and an increase in free Trp levels in the plasma or serum of nephrotic children. We, therefore, examined the change of serum Trp levels following the development and recovery of acute nephrosis in 6-week-old male Wistar rats injected once with puromycin aminonucleoside (100mg/kg body weight) and checked the levels of 16 amino acids including Trp in the serum and the levels of Trp in the liver, kidney, and urine under nephrotic conditions. In this study, the development and recovery of nephrosis were checked by the changes of levels of urinary protein and serum protein and albumin. Total serum Trp and albumin-bound serum Trp levels decreased with the development of nephrosis and these decreased levels returned to the normal level with its recovery. In contrast, free serum Trp levels increased with the development of nephrosis and this increased level returned to the normal level with its recovery. In the serum of nephrotic rats, the decrease of albumin-bound Trp levels and the increase of free Trp levels were well consistent with a decrease in albumin levels and an increase in the level of non-esterified fatty acids which are known to weaken the binding of Trp to albumin and among 16 amino acids studied, only Trp showed a significant change in its levels. Trp levels increased in the liver and kidney but not in the urine under nephrotic conditions. These results indicate that the change of serum Trp levels should be closely related to the condition of nephrosis and that although serum Trp is lost under nephrotic conditions, the lost serum Trp is accumulated in the liver and kidney.