Oral administration of oxalate-enriched spinach extract as an improved methodology for the induction of dietary hyperoxaluric nephrocalcinosis in experimental rats

Experimental induction of hyperoxaluria by ethylene glycol (EG) administration is disapproved as it causes metabolic acidosis while the oral administration of chemically synthesized potassium oxalate (KOx) diet does not mimic our natural system. Since existing models comprise limitations, this study is aimed to develop an improved model for the induction of dietary hyperoxaluria, and nephrocalcinosis in experimental rats by administration of naturally available oxalate rich diet. Male albino Wistar rats were divided into five groups. Group I, control; group II rats received 0.75% EG, group III rats fed with 5% KOx diet and group IV and V rats were administered with spinach extract of 250 and 500 mg soluble oxalate/day respectively, for 28 d. Urine and serum biochemistry were analyzed. After the experimental period, rats were sacrificed, liver and kidney tissue homogenates were used for antioxidant and lipid peroxidation assay. Relative change in expression of kidney injury molecule-1 (KIM-1) and crystal modulators genes in kidney tissues were evaluated. Tissue damage was assessed by histology studies of liver and kidney. Experimental group rats developed hyperoxaluria and crystalluria. Urine parameters, serum biochemistry, antioxidant profile, lipid peroxidation levels and gene expression analysis of experimental group II and III rats reflected acute kidney damage compared to group V rats. Histopathology results showed moderate hyperplasia in liver and severe interstitial inflammation in kidneys of group II and III than group V rats. Ingestion of naturally available oxalate enriched spinach extract successfully induced dietary hyperoxaluria and nephrocalcinosis in rats with minimal kidney damage.