Abstract
Purpose: It is well-recognized that dietary factors may influence in the pathogenesis of urinary lithiasis (UL), the third most prevalent disorder of the urinary tract. Herein we evaluated the effects of the dietary supplementation with vitamin D, which has been recently associated with hypercalcemia, on the occurrence of UL in rats that developed chronic hyperoxaluria after exposition to ethylene glycol, an inducing agent. Materials and method: Thirty Sprague-Dawley male rats were randomly divided into three groups: Group 1 (control, n=10); Group 2 (0.5% ethylene glycol+vitamin D3, n=10); Group 3 (1.25% ethylene glycol, n=10). Urine samples were collected over a 24 h period at the baseline (day zero) and weekly during four weeks for the dosage of calcium, oxalate, uric acid, citrate and serum creatinine. Animals were euthanized, their right kidneys removed and the corresponding hematoxylin-eosin staining of the histological sections subjected to histological/ histomorphometric analyses using the Image J® software. The deposition of calcium salts in the renal parenchyma was quantified by the PIXE technique (Proton Induced X-Ray Emission). Results: All animals displayed normal levels of serum creatinine (median 0.6 mg/dl) and no statistical difference was found in the daily fluid intake. The volume of the urine samples was significantly higher in animals from G2 when compared to the control animals (10.1 mL versus 4.5 mL, p<0.05). Except for hyperoxaluria, which was observed for G3 animals, all the other parameters showed no significant variation after four weeks. In the histomorphometric analysis, nephrocalcinosis was observed for G2 (15 crystals/animal), being the deposition of calcium salts in the renal parenchyma of these animals 100 times higher than the observed for rats from G3 or from the control group. Conclusion: Although the association of vitamin D3 with ethylene glycol (EG) at 0.5% did not substantially increase the levels of urinary oxalate as observed for EG alone at 1.25%, this association significantly increased the histological damage of the renal parenchyma via nephrocalcinosis.
Highlights
Urinary lithiasis (UL) is the third most prevalent disorder of the urinary tract after urinary infections and prostate disorders [1]
Conclusion: the association of vitamin D3 with ethylene glycol (EG) at 0.5% did not substantially increase the levels of urinary oxalate as observed for EG alone at 1.25%, this association significantly increased the histological damage of the renal parenchyma via nephrocalcinosis
Considering that some of the most common types of kidney stones are composed predominantly of calcium oxalate (CaOx) [8], effective models of chronic hyperoxaluria can be produced in rats through the use of inducing agents, such as ethylene glycol (EG), which promote crystalluria and the consequent deposition of CaOx crystals in the renal parenchyma [9,10]
Summary
Urinary lithiasis (UL) is the third most prevalent disorder of the urinary tract after urinary infections and prostate disorders [1]. Urinary crystallization occurs due to abnormalities in the composition of the urine, either by an excessive excretion of promoter agents (e.g. calcium, oxalate, uric acid, etc.), by the reduced excretion of inhibitors (such as citrate, magnesium, glycosaminoglycans and Tamm-Horsfall protein), or both [2,3,4]. Considering that some of the most common types of kidney stones are composed predominantly of calcium oxalate (CaOx) [8], effective models of chronic hyperoxaluria can be produced in rats through the use of inducing agents, such as ethylene glycol (EG), which promote crystalluria and the consequent deposition of CaOx crystals in the renal parenchyma [9,10].
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