[Urinary peptides and calcium oxalate nephrolithiasis, a combined approach: MALDI-TOF mass spectrometry and MicroBCA Protein Assay]

Urinary lithiasis is one of the most common benign urological diseases. There is growing evidence that a delicate equilibrium regulated by the function of proteins, soluble peptides, membrane proteins and intracellular mechanisms actually exists. We have studied the urinary protein composition of patients affected by calcium oxalate nephrolithiasis in order to discover a biomarker or any predisposing factors. The urinary protein composition of 17 patients (11 males, 6 females; mean age 45yrs ± 14SD), affected by calcium oxalate nephrolithiasis, was assessed in comparison with 17 healthy subjects. A qualitative assay was performed using MALDI-TOF mass spectrometry in a spectrum between 1 and 5kDa (medium size peptides), and a numerical (quantitative) assay using specific filters and MicroBCA Protein Assay. No differences were detected in the mass spectrums between patients and control subjects: all peaks overlapped perfectly. The results of the numerical assay suggest that concentrations of protein species <5kDa in control samples were actually higher than those which were found in patients. The differences are statistically significant. The study detected neither a biomarker nor any predisposing factors in "stone former" patients. The assessment of the results obtained, in terms of quantitative differences, indicate the need for further research.