Studies On Mechanism Of Calcium Oxalate Stone Formation In Canines

The incidence of calcium oxalate (CaOx) crystals in dog’s urine may be an arising problem in different countries over the world. Oxalate and/or oxalic acid are suspected to be the major elements involved in the development of CaOx crystalluria and calcium oxalates crystals induce sever injury to renal tissue. The renal dead epithelial cells act as a nidus for the accumulation and aggregation of crystals in the tubules ended by renal stone formation and renal failure. This study was designed to investigate the deleterious effects of KOx injection on the urinary system and the validity of using KOx as a model of induction of CaOx crystalluria and renal oxalosis in dogs by studying the effect of KOx on the following:(1) Serum and urine biochemical profiles including liver and kidney function tests, serum and urine electrolyte concentrations and urinary sediment microscopical.(2) Morphological changes of the renal tissue including ultrasonography, histopathology, scanning electron microscopy (SEM), and detection of the cellular ultrastructural changes by transmission electron microscopy (TEM).(3) Changes of two important macromolecules:osteopontin (OPN) and Tamma-Horsfall (THP) proteins through immunohistochemical localization and quantitative Real-time-polymerase chain reaction (qPCR) for accurate quantification.The main results were as follows:(1) There were significant gradual increases in the serum creatinine and BUN in the treatment group on days0,1,3and5of injection, compared with control group. Urinary creatinine and urinary urea nitrogen decreased gradually in the treatment group, compared to the control. Urine sediment examination showed COD and COM crystals in the urine of the treated dogs with KOx.(2) Ultrasonographic images revealed a mild hyperechogenicity in cortical renal tissue and showed significant increases in the BPL and MW of both left and right kidneys after treatment. The histopathological findings recorded the deposition of oxalate crystals in the renal tissues。Crystals induced severe tubular injury. The SEM of kidney tissue illustrated that crystals were bound to the injured epithelial cells of the renal tissue in the treated dogs and X-ray analysis of these crystals revealed high calcium content. TEM examination found that excessive cytoplasmic vacuolization, clubbing of microvilli, collapsed mitochondria and appearance of crystals ghosts inside cells and in the tubular lumen.(3) Immunohistochemical staining of renal tissue sections revealed a remarkable increase in the intensity and spread of OPN staining in the treatment group. Surprisingly, staining for THP in the treatment group relatively decreased, compared to control group in the TAL of the inner cortex and outer medulla. Quantitative PCR revealed a significant induction of OPN mRNA and a significant decrease in THP mRNA expression level.In conclusion usage of KOx intravenous injection successfully induced a condition if calcium oxalate crystalluria in dogs and large area of kidney epithelial cell were damage, eventually leading to decline in renal function, blood urea nitrogen and creatinine levels, blood urea nitrogen and creatinine levels in the urine decreased. The adhesion of the precipitated crystals of calcium oxalate renal tubular epithelial cells reduced the level of THP expression in and increased the expression of OPN level.