Toward proteomics in uroscopy: Urinary protein profiles after radiocontrast medium administration

Previous attempts to use urinary protein profiles for diagnostic purposes h ave been rather disappointing with re spect to their clinical validity, in part because of the insufficient reproducibility, sensitivity, and rapidity of available techniques. Therefore, a newly developed, high-throughput tec hnique, namely surface-enhanced laser desorption/ionization (SELDI) Protein Chip array-time of flight mass spectrometry, was studied, to assess its app licability for protein profiling of urine and to exemplify its use for a gr oup of patients receiving radiocontrast medium. Assessment of the accuracy, sensitivity. and reproducibility of SELDI in test urinary protein profilin g was performed. Renal function was studied in 20 male Sprague-Dawley rats before and after intravenous administration of either 1.25 g/kg ioxilan (n = 10) or hypertonic saline solution (n = 10) as a control. Urine samples fr om 25 patients undergoing cardiac catheterization were obtained before. imm ediately after, and 6 to 12 h after the procedure. Administration of ioxila n to rats resulted in changes in the abundance of proteins of 9.9, 18.7, 21 .0, and 66.3 kD. For patients, even in uncomplicated cases of radiocontrast medium infusion during cardiac catheterization, perturbations in the prote in composition occurred but returned to baseline values after 6 to 12 h. Pr oteins with molecular masses of 9.75, 11.75, 23.5, and 66.4 kD changed in a bundance. For patients with impaired renal function, these changes were not reversible within 6 to 12 h. As a proof of principle, one of the peaks, i. e., that at 11.75 kD, was identified as beta (2)-microglobulin, SELDI is a promising tool for the detection, identification. and characterization of t ract amounts of proteins in urine. Even for patients without renal complica tions, proteins with a broad range of molecular masses either appear in or disappear from the urine. Some of these might represent markers of impendin g nephropathy.