Study of a rat model for calcium oxalate crystal formation without severe renal damage in selected conditions

Abstract

Background : Although nephrotoxic in high doses, ethylene glycol (EG) has been used with ammonium chloride (NH 4 Cl) or vitamin D 3 to study calcium oxalate stone formation in rat models. In the present study we used EG alone or with NH 4 Cl to study hyperoxaluria, crystaluria, and crystal attachment to renal epithelial cells in rats with minimal renal damage . Methods : Six-week-old male Sprague-Dawley (SD) rats were given food and special drinking water.In experiment 1 the drinking water contained 1.0% NH 4 Cl plus four different concentrations of EG (0.8%, 0.4%, 0.2%, 0.1%). In experiment 2 the drinking water contained EG alone (0.8%, 0.4%, 0.2%, 0.1%). Urine was collected for 24 h before the rats were sacrificed. In experiment 1 the rats were sacrificed 5-13 days after starting the special water. In experiment 2 the rats were sacrificed 7-21 days after starting the special water. Bladder urine was also obtained. Blood and urine were tested for calcium, phosphorus, and creatinine. In addition, urine was tested for pH, oxalate and Nacetyl-b -D glucosaminidase (NAG). Kidney sections were stained with hematoxylin-eosin, von Kossa and Pizzolato stain. Crystal morphology was determined using polarizing microscopy, and composition was determined using high-resolution X-ray powder diffraction . Results : Experiment 1: Aggravation of renal function, an increase in urinary oxalate and NAG excretion, and crystals observed in the kidneys all correlated with EG concentration and length of drinking time. In bladder urine, calcium oxalate monohydrate (COM) crystals exceeded calcium oxalate dihydrate (COD) crystals. Experiment 2: Renal function remained unchanged. Oxalate excretion increased and NAG increased slightly. Crystals occurred only in the papillary tip region. Crystals in bladder urine were mostly COD . Conclusion : In the current rat model, calcium oxalate crystaluria could be induced without severe renal damage in selected cases. Either and/or both COM and COD might form and interact with kidney epithelium. We propose different experimental conditions to study the various phases of calcium oxalate stone formation in young male SD rats.

Intracrystalline urinary proteins facilitate degradation and dissolution of calcium oxalate crystals in cultured renal cells

“…The activities of NAG and ␤-galactosidase (3,21) and also those of ␣-glucosidase and ␥-glutamyl transpeptidase (3) are elevated in urine from stone patients, as is the level of an unidentified serine protease that cleaves OPN (4). Similar changes accompany nephrocalcinosis induced in hyperoxaluric rats (24,25,56), in which COM crystal formation is associated with significant, proportional increases in urinary oxalate and activity of NAG and the brush-border enzymes alkaline phosphatase, leucine aminopeptidase, and ␥-glutamyl transpeptidase (24,25,56).…”

Helichrysum plicatum DC. subsp. plicatum extract as a preventive agent in experimentally induced urolithiasis model

“…CaOx is the primary constituent, which is found in the urine of urolithiasis patients (Yamaguchi et al, 2005). Various in vivo methods and therapeutic agents were used to illuminate the development and progression of the disease .…”

In vivo efficacy of Trachyspermum ammi anticalcifying protein in urolithiatic rat model

“…To induce CaO x crystal formation in rats, they were exposed to 0.4% ethylene glycol (EG) with 1.0% ammonium chloride (NH 4 Cl) in their drinking water for 9 days (Yamaguchi et al, 2005). All rats were divided into four groups having 8 rats each, named as group 1, group 2 and group 3.…”