Dietary tryptophan supplementation prevents proteinuria in the seven-eighths nephrectomized rat

Surgical reduction of renal mass in the rat leads to proteinuria, hypertension, and progressive renal failure beyond that of the original physical destruction of renal mass. Both hypertension and proteinuria have been implicated in the process of progression of renal failure. The seven/eighths nephrectomized rats fed a diet supplemented with 4% tryptophan (UT) had a urinary albumin excretion rate of 0.055 +/- 0.056 mg/100 g body weight/hr compared to 0.02 +/- 0.029 mg/100 g body weight/hr in control rats, whereas the nephrectomized rats fed a regular diet (UR) excreted 1.12 +/- 0.730 mg/100 g body weight/hr (P less than 0.001). Hypertension was also prevented in the UT group but not in the UR group. Once hypertension and proteinuria were established during maintenance on a regular diet, they were not reversed by subsequent dietary tryptophan supplementation. If dietary tryptophan supplementation is continued, however, the progressive histopathology that develops after seven-eighths nephrectomy is not prevented despite avoidance of proteinuria and hypertension.