Analysis of α2u-Globulin in Rat Urine and Kidneys by Liquid Chromatography−Electrospray Ionization Mass Spectrometry

A quantitative method was developed for determination of α2u-globulin in urine and kidney samples collected from male rats using liquid chromatography−electrospray ionization mass spectrometry (LC−ESI/MS). Samples prepared from urine and kidney homogenates using size exclusion filters were subject to reversed-phase liquid chromatography and the effluent passed into an electrospray ionization source. Quantitative analysis using external standard calibration was based upon selected ion monitoring of protonated molecular ions by the mass spectrometer. Linear calibration curves were developed over the range of ∼4.6−370 μg of α2u-globulin/μL for spiked urine standards and over the range of ∼4.6−550 μg of α2u-globulin/μL for spiked kidney standards. The precision (relative standard deviation) for repeated injection (using urine samples) and intra-assay precision (using both urine and kidney samples) were within ±10.4% and ±13.2%, respectively. Using spiked urine standards, inter-assay precision, intra-assay acc...