Tryptophan glycoconjugate as a novel marker of renal function

PURPOSE: Neither serum creatinine concentration nor creatinine clearance as sess renal function accurately. Serum creatinine concentration is affected by muscle mass, and the creatinine clearance overestimates the glomerular f iltration rate because of tubular secretion of creatinine. The present stud y was designed to determine whether serum concentrations of 2-(alpha -manno pyranosyl)-L-tryptoyhan (MPT), a tryptophan glyco-conjugate, can be used as a marker of renal function. METHODS: Clearances of MPT and of inulin were compared in normal rats and i n rats with cisplatin-induced acute renal failure. We also compared the cle arances of MPT and of creatinine with inulin clearance in 25 patients with chronic renal disease. Serum concentrations of MPT and creatinine as a func tion of MPT clearance were determined in 108 patients with chronic renal di sease. RESULTS: There was strong linear correlation between clearances of MPT and inulin in rats (r = 0.97) and humans (r = 0.87), indicating that renal hand ling of MPT is similar to that of inulin. In humans, linear regression anal yses indicated that MPT was a better indicator of inulin clearance than was creatinine clearance. At the same level of renal function, serum creatinin e concentrations tended to be lower in patients with less muscle mass las i ndicated by a urinary creatinine excretion <1,000 mg in 24 hours) than in t hose who excreted > 1,000 mg in 24 hours, whereas serum MPT concentrations were not affected by creatinine excretion. CONCLUSION: MPT clearance can replace inulin clearance in the clinical sett ing. The serum MPT concentration is an accurate measure of renal function e ven in patients with diminished muscle mass, and thus is a better indicator of renal function than is the serum creatinine concentration. (C)2001 by E xcerpta Medica, Inc.