Effects of high-sodium diet on lithogenesis in a rat experimental model of calcium oxalate stones

BACKGROUND: This study aimed to investigate the effects of a high- and low-sodium diets on lithogenesis in a rat experimental model of calcium oxalate stones. METHODS: Twenty male Wistar rats were randomly divided into four groups; group A: 4% NaCl+1% ethylene glycol (EG); group B: 8% NaCl+1% EG; group C: 8% NaCl+normal drinking-water; group D: 1% EG +normal diet. All rats were sacrificed 4 weeks later, and blood samples were collected from the heart. The kidneys were collected for Von Kossa staining to evaluate the formation of calcium-containing crystals. The last 24-h urine samples were also gathered for metabolic analysis. RESULTS: Von Kossa staining demonstrated that the rats in both group A and group B had significantly more renal calcium crystals than those in group D. However, 24-h urinary volume increased significantly (142.26±20.91 mL) in group B compared with group A (100.52±28.23 mL), group C (107.36±14.24 mL), group D (40.79±8.71 mL) (P=0.004, 0.012, and 0.000 respectively). Level of urine sodium (Na), potassium (K), chlorine (Cl), and calcium (Ca), urea nitrogen were significantly higher in group B compared with group D. The urine phosphorus, oxalate, and creatinine levels; urine specific gravity; and urine PH were similar between group B and group D. The level of serum sodium was higher in group B (151.26±4.06 mmol/L) compared with group D (145.56±1.12 mmol/L) (P=0.002). CONCLUSIONS: A high sodium intake might increase the risk of lithogenesis in susceptible individuals (given by EG) or in individuals with water restriction.