Proteomic analysis of the renal medulla of Dahl salt‐sensitive rats and consomic SS‐13BN rats

The consomic SS‐13 BN rat, genetically identical to the Dahl salt‐sensitive (SS) rat except chromosome 13, exhibited a substantial reduction of blood pressure salt‐sensitivity. The present study utilized a proteomic approach to identify proteins that might contribute to the phenotypic differences between SS and SS‐13 BN . Differential in‐gel electrophoresis analysis of the renal medulla indicated that of approximately 2200 spots analyzed, 58 spots exhibited differential expression between 6‐week old SS and SS‐13 BN rats on a 0.4% NaCl diet (n=4, P<0.05, ratio >1.2 or <−1.2). MALDI‐TOF‐MS analysis successfully identified 42 spots, representing 28 unique proteins, 4 of which are encoded by genes located on chromosome 13. Western blot analysis confirmed the differential expression of 3 proteins (n=4, P<0.05) including fumarase (1.65 ± 0.12 fold higher in SS), heterogeneous nuclear ribonucleoprotein K (2.40 ± 0.32 fold higher in SS), and superoxide dismutase 1 (1.1 ± 0.03 fold higher in SS‐13 BN ). Moreover, fumarase, which catalyzes the inter‐conversion of fumarate and malate, exhibited a significant shift of isoelectric point toward the basic side in SS. The specific activity of fumarase was 1.89 ±0.14 fold lower in the renal medulla of SS (n=4, P<0.01). The present study provided new insights into the molecular basis for the phenotypic differences between SS and SS‐13 BN . (NIH R01HL077263 and N01‐HV‐28182)