The Effect Of Hyperoxaluria On Urinary Calcium Excretion, And The Oxidative Damage Of Hyperoxaluria On TRPV5 Which Present InEpithelial Cells Of Renal Distal Tubule And Collecting Duct

Objective:1. To explore the effect of hyperoxaluria on urinary calcium excretion; 2. To investigate the effect and possible mechanism of hyperoxaluria on the calcium transport system and the transient receptor potential cation channel V5(TRPV5) in distal and collecting tubule; 3. To discuss the possibility of potassium citrate in reducing the urinary calcium levels and reducing risk of lithogenesis by protecting TRPV5.Methods:1. We retrospectively investigated whether hyperoxaluria patients were complicated with urinary calcium excretion increased. And then a linear regression analysis was performed to comprehend the relevance and related degree of hyperoxaluria and increased urinary calcium excretion.2. We explore the correlation between different concentrations of urinary oxalate and urinary calcium excretion levels in hyperoxaluria animal model.3. We detected the superoxide dismutase (SOD) and malondialdehyde (MDA) concentration in kidney and histopathological examination HE staining of kidney tissue, to observe the oxidative stress injury of rats’renal tubular epithelial cells under different concentrations of urinary oxalic acid. 4. We observed the TRPV5 mRNA expression by QPCR and TRPV5 protein assay by Western-blot to understand the effect of urinary oxalate concentrations on TRPV5’s quantities and activities of rat’s kidney.5. We discussed the validity and possible mechanism of potassium citrate in reducing the urinary calcium levels by animal experiments.Results:1. Retrospective clinical study shows:In patients with calcium oxalate stones, urinary calcium levels in patients with hyperoxaluria is higher than normal urinary oxalate patients and the difference was statistically significant (P=0.022), and this phenomenon presents both males and female patients. Urinary calcium excretion increased with urinary oxalate increasing, when urinary oxalate levels> 40mg/24h (r=0.321, weak correlation), and conform to linear correlation (equation of linear regression:Y=1.795X+130.106, P=0.037). This linear relationship does not exist when urinary oxalate levels> 100mg/24h.2. Animal experiments can be seen: Urinary oxalate, urinary calcium increased with the glycol concentration increasing in each group of rats (P<0.05). And urinary calcium excretion is positively correlated with urinary oxalate. Animal experiments can also be seen:Oxidation product MDA content gradually increased and the antioxidant product -- SOD content decreased gradually while with the increasing of urinary oxalate concentration, and the difference was statistically significant (P<0.05). Kidney tissues HE staining microscopy show:With the increased of urinary oxalate concentration, renal cortex and medulla congestion aggravating gradually, proximal convoluted tubules and renal interstitial edema aggravation gradually, the number of distal convoluted tubule crystallization and inflammatory cells infiltration degree are increasing, the number of renal papillary duct crystallization is increasing, renal calyx shedding cells numbers are increasing.4. QPCR result can be seen, the expression of TRPV5 mRNA increased gradually when the urinary oxalate concentration reduced. Western-blot results also can be seen. TRPV5 protein increases gradually when urinary oxalate concentration decreases, and the difference was statistically significant (P<0.05).5. Compared with 1% EG group, rats with 1% EG+ calcium potassium citrate group urinary calcium excretion decreased, MDA content decreased, SOD content increased, TRPV5 mRNA and protein levels have rebounded and the difference was statistically significant (P<0.05).Conclusions:1. Hyperoxaluria can cause urinary calcium excretion increase; 2. Hyperoxaluria leads to urinary calcium excretion increase may be due to: hyperoxaluria can caused renal tubular epithelial cells from oxidative injury, and the distal tubule and collecting duct epithelium cells TRPV5 content and activity decreased, resulting in urinary calcium reabsorption decrease and thus increase urinary calcium excretion.3. Potassium citrate has certain effect in inhibition of hypercalciuria which caused by hyperoxaluria.