Even slightly decreased dietary salt Intake suppresses progression of renal insufhcieny in rats with 5/6 nephrectomy
Abstract
Background: Ablation of 5/6 renal parenchyma (ablation nephropathy) is an experimental model of chronic kidney failure. The residual nephrons respond with the increase of intraglomerular pressure, glomerular filtration rate, development of proteinuria, systemic hypertension, and chronic renal failure.
For a long time, it has been known that decrease in salt intake decreases systemic blood pressure. Newly discovered evidence shows that the lower salt intake decreases a formation of tissue injury mediators (ADMA, PDGF, IL-I, reactive oxygen species etc.).
The aim of our study was to compare the ablation nephropathy progression in 5/6 nephrectomized rats fed diet with a standard and decreased salt intake. Materials and methods: Seventy seven female inbred AVN rats and 84 SPF Wistar rats aged 12 weeks were included in the study.
We performed nephrectomy of the right kidney and a resection of the 2/3 of the left kidney parenchyma in pentobarbital anesthesia. We measured systolic blood pressure, serum and urinary creatinine and sodium concentration, urine volume and proteinuria before the operation, and at 4, 7 and 10 week after the operation in AVR strain, and in SPF Wistar strain also at 14 and 17 week.
Glomerular injury score (GIS) was determined at the end of the experiment. The rats were fed standard and low salt diet throughout the experiment.
Results: Differences between measured parameters in rats on standard resp. low salt diet are as follows: median sodium intake 31 resp. 22 mg/24 h; renal parenchyma mass at the end of experiment 1.40 +- 0.34 g resp. 1.20 +- 0.25 (P < 0.01); systolic blood pressure 151 +- 29 mmHg vs. 126 +-21 (P < 0.01 ); serum creatinine levels 164 +- 84 resp. 106 +- 29 umol/l (P < 0,01 ); proteinuria 179 +- 78 resp. 178 +- 85 mg/24 h (N.S.); GIS 2.06 +- 0.48 resp. 1.43 +- 0.62 (P < 0.01). The findings in SPF Wistar strain of rats resembled those in AVN strain but differences did not reach statistical significance.
Conclusion: In rats with 5/6 nephrectomy fed diet with decreased salt content, we found smaller hypertrophy of the residual renal parenchyma, lower serum creatinine level, lower systolic blood pressure and less progressed mesangial sclerosis.