title: Differential expression of proteins in renal cortex and medulla: a proteomic approach.
abstract: BACKGROUND
  Western blotting has previously been used to identify changes in protein expression in renal tissue. However, only a few proteins can be studied in each experiment by Western blot. We have used proteomic tools to construct protein maps of rat kidney cortex and medulla.
  
  
  METHODS
  Expression of proteins was determined by silver stain after two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Protein spots were excised and digested with trypsin. Peptide masses were identified by MALDI-TOF mass spectrometry. The Mascot search engine was used to analyze the peptide masses and identify the proteins.
  
  
  RESULTS
  Seventy-two proteins were identified (54 unique proteins) out of approximately 1000 spots visualized on each gel. Most of the spots were expressed both in cortex and medulla. Of the identified proteins, three were expressed only in medulla and one only in cortex. Nine proteins were expressed in both regions but to a greater extent in cortex and three proteins were expressed more in medulla. Differential expression was confirmed for three proteins by Western blot.
  
  
  CONCLUSIONS
  A large group of proteins and their relative expression levels from cortical and medullary portions of rat kidneys were found. Sixteen proteins are differentially expressed. Proteomics can be used to identify differential expression of proteins in the kidney on a large scale. Proteomics should be useful to detect changes in renal protein expression in response to a large range of physiological and pathophysiological stimuli.
authors.affiliation: Department of Medicine, University of Louisville, Louisville, KY, USA. arthurj@musc.edu
authors.forename: John M
authors.initials: JM
authors.lastname: Arthur
authors.forename: Visith
authors.initials: V
authors.lastname: Thongboonkerd
authors.forename: Janice A
authors.initials: JA
authors.lastname: Scherzer
authors.forename: Jian
authors.initials: J
authors.lastname: Cai
authors.forename: William M
authors.initials: WM
authors.lastname: Pierce
authors.forename: Jon B
authors.initials: JB
authors.lastname: Klein
mesh_terms: D000818:Animals; D015180:Electrophoresis, Gel, Two-Dimensional; D007672:Kidney Cortex / Q000737:chemistry* / Q000502:physiology*; D007679:Kidney Medulla / Q000737:chemistry* / Q000502:physiology*; D011506:Proteins / Q000032:analysis; D040901:Proteomics / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D011506:Proteins