Approval of the method of electrophoretic separation and identification of some urine proteins in rats with toxic nephropathy
Authors: Sivak Konstantin V. , Zabrodskaya Yana A. , Dobrovolskaya Olga A. 
Published: January 2020

The aim of the article. The aim was to test the method for determining certain protein markers in rat urine by electrophoretic separation followed by mass spectrometric identification for early diagnostic of nephrotoxicity. The objectives of the study included assessing the reproducibility of the protein separation method, comparing rats urine protein profiles normal and after gentamicin sulfate administration, as well as a biochemical and morphological study of kidney biopsy specimens.
Materials and methods. Gentamicin sulfate (GS) was administered intramuscularly to rats of both sexes at a dose of 60 mg/kg b.w. for consequence 5 days. Daily urine was collected in the background, on the 3rd, 7th and 14th day from the start of the administration of GS in the metabolic cages. We measured the concentrations of total protein and creatinine in urine samples, the level of lipids in the homogenates of the kidneys. Electrophoretic separation of urine proteins was performed in the Mini-PROTEAN Tetra Vertical Electrophoresis. The gels were stained, and the stained zones were excised and enzymatic hydrolysis of the proteins was performed. Spectra of tryptic peptides were recorded on an ultrafleXtreme MALDI-TOF/TOF mass spectrometer (Bruker, Germany). Proteins were identified in the Biotools program by accessing the Mascot database (matrixscience.com).
Results. Assessment of reproducibility of the results of electrophoretic separation of rat urine proteins showed an acceptable value of the coefficient of variation (on average 8.03%) and the error of analysis (analysis = 14.53%). It that normally in rats of males the alpha-2-uroglobulin precursor dominates in urine and in females immunoglobulin G light chains dominate was show. Against the background of the administration of GS, leukocytes in pathological concentrations appear in the urine in rats of both sexes; in males, the proteomic profile has a strong intraspecific dispersion, including due to sperm contamination; in females, well identified zones of albumin, alpha-1-antitrypsin, aminopeptidase M, beta-2-microglobulin, and transferrin was appear. A biochemical study of kidney homogenates an increase in total cholesterol (males) and triacylglycerides (females) revealed. Pathomorphological changes were similar in male and female rats in the form of fatty degeneration of the proximal tubule nephrothelium and leukocyte infiltration of interstitium and confirmed changes in the spectrum of urine proteins.
Conclusion. Based on the analysis of the experimental results it was found that the use of the technology of electrophoretic separation of proteins in PAGE under denaturing conditions followed by MALDI mass spectrometric identification (PAGE-MALDI-TOF/TOF) and densitometric determination of the percentage of protein fractions is applicable for the detection of nephrotoxicity. Due to gender differences in the protein spectrum it is preferable to examine the urine of female rats. Pathomorphological changes did not have gender differences.