Renal regional proteomes in young Dahl salt-sensitive rats

We performed an extensive proteomic analysis of the Dahl model of salt-sensitive hypertension. The consomic SS-13(BN) rat, genetically similar to the Dahl salt-sensitive rat, while exhibiting a significant amelioration of salt-induced hypertension, was used as a control. Proteomic analysis, using differential in-gel electrophoresis and mass spectrometry techniques, was performed in the renal cortex and the renal medulla of 6-week-old SS and SS-13(BN) rats before significant differences in blood pressure were developed between the 2 strains of rat. Several dozen proteins were identified as differentially expressed between SS and SS-13(BN) rats fed the 0.4% NaCl diet or switched to the 4% NaCl diet for 3 days (n=4). The identified proteins were involved in cellular functions or structures including signal transduction, energy metabolism, and the cytoskeleton. The proteomic analysis and subsequent Western blotting indicated that heterogeneous nuclear ribonucleoprotein K in the renal medulla was upregulated by the 4% NaCl diet in SS-13(BN) rats but downregulated in SS rats. The level of angiotensinogen mRNA in the renal medulla was regulated in an opposite manner. Silencing of heterogeneous nuclear ribonucleoprotein K resulted in an upregulation of angiotensinogen in cultured human kidney cells. In summary, we identified significant differences in kidney regional proteomic profiles between SS and SS-13(BN) rats and demonstrated a potential role of heterogeneous nuclear ribonucleoprotein K in the regulation of angiotensinogen expression in the renal medulla.