DIFFERENTIAL EXPRESSION OF CYTOSOLIC PROTEINS IN THE RAT-KIDNEY CORTEX AND MEDULLA - PRELIMINARY PROTEOMICS

The rodent kidney is a target of many xenobiotics and is typified by r egionally specific structure and function. This renders distinct regio ns of the kidney differentially susceptible to toxic exposure and effe ct. To characterize these differences at the proteome level, protein p atterns from male rat kidney cortex and medulla cytosols were examined by two-dimensional electrophoresis (2-DE) and image analysis and prom inent proteins identified immunologically or by matrix-assisted laser desorption/ionization - mass spectrometry (MALDI-MS) and electrospray/ ionization - tandem mass spectrometry (ESI-MS/MS) sequence tag identif ication. An average of 727 protein spots were resolved and matched to the cortex cytosol reference pattern, and 716 in the medulla. Of this total, 127 proteins were found to differ in abundance (86 higher in co rtex; 41 higher in medulla) (P < 0.001). Of those proteins that were d etectable in both cortex and medulla, the abundance of 97 differed sig nificantly while 30 proteins were found to be unique to one region or the other (26 in cortex, 4 in medulla). Twenty protein spots were iden tified and their regional differences are discussed. These results bot h confirm and expand our understanding of the molecular heterogeneity characterizing structurally and functionally distinct regions of the k idney and serve as a useful foundation for future nephrotoxicologic st udies.