Effect Of Total Saponins Of Dioscorea On Expression Of Uric Acid Transporters In Hyperuricemia Rats

Background: Hyperuricemia is an important biochemical basis of uric acid renaldamage and gouty arthritis. Research has shown that,90%hyperuricemia is due to thereduced excretion of uric acid by. Uric acid rely mainly on renal tubular epithelial cellbrush border on the side of the kidney excretion （luminal membrane） and basolateralmembrane fixed transporter, which is responsible for uric acid reabsorption of urateanion transporter1（URAT1）, and is responsible for uric acid secretion of organic aniontransporter （OAT1and OAT3） etc.Total saponins of Dioscorea （TSD） is a kind ofeffective components extracted from Dioscorea plant Dioscorea septemloba Thunb in,the main active component is the steroidal saponins. The theory of traditional Chinesemedicine, Dioscorea taste bitter, flat, with dampness and removing turbidity,qufengchubi effect, is a Chinese representative clinical medicine for treatinghyperuricemia. But on the total saponins of Rhizoma Dioscoreae colletii （TSD） onhyperuricemia mechanism has not been reported.Objective: prevention and treatment effects of total saponins of Dioscorea onhyperuricemia rats and the effect on the expression of renal tubule urate transporter。Methods:90male SD rats,15were randomly selected as the control group, the otherrats with adenine100mg·kg^-1+ethambutol250mg·kg^-1ig,1times a day, for6consecutive weeks. From the fourteenth day rat orbital blood, serum uric acid level.According to the serum uric acid values the rats were randomly divided into modelgroup, total saponins of Dioscorea high (300mg·kg^-1), in (90mg·kg^-1), and low (30mg·kg^-1) dose group, benzene bromine Malone group (10mg·kg^-1). Group administered orally,1times a day, for28consecutive days. In administration of13-14days,27-28days of urine, collection of24h rat urine, the urine volume was recorded, determinationof rat urine uric acid, creatinine and uric acid excretion. Administration for14days,28days, blood samples were taken for measurement of rat serum uric acid, xanthineoxidase （XOD）, creatinine and urea nitrogen, creatinine clearance was calculated, uricacid clearance. Renal tissues were stained by HE renal pathological observation,immunohistochemical method for the determination of URAT1in renal tubularepithelial cells （renal uate-anion exchanger）, OAT1（organic anion transporter1）, OAT3（organic anion transporter3） expression. The other clipping renal cortex in liquidnitrogen preservation, expression of RT-PCR method for detection of URAT1mRNA inrenal tubular epithelial cells.Result：Compared with normal rats, adenine and ethambutol gavage for14days, the rats makeserum uric acid （UA）Levels were significantly increased （P<0.01）. After grouping,groups continue to molding agent, compared with the normal group, after medication,、serum uric acid levels of rats in model group(μmol·L^-1,276.5±68.0vs104.7±15.66,266.3±83.0vs108.4±14.94,P<0.01),uric acid concentration(μmol·L^-1,1638.6±317.7vs1009.3±311.17,1601.4±392.5vs971.7±222.35,P<0.01),24hours uric acid excretion（μmol,26.9±5.6vs16.4±3.88,27.1±6.2vs17.5±3.33,P<0.01）,uric acid clearance（ml·min-1,0.070±0.0vs0.110±0.03,0.075±0.0vs0.113±0.02）, serum creatinine （Cr）(μmol·L^-1,87.9±10.5vs58.6±6.72,92.1±8.2vs58.9±6.51, P<0.01), creatinine clearancerate （ml·min-1,0.918±0.218vs1.590±0.352,0.843±0.113vs1.666±0.229）, blood ureanitrogen （BUN）,(mmol·L^-1,9.89±3.01vs4.91±0.46,11.40±2.85vs5.00±0.48, P<0.01),xanthine oxidase （XOD） activity (U·L^-1,31.42±6.15vs19.17±3.20,30.52±6.82vs18.05±2.45,P<0.01), significantly increased. Renal proximal tubule epithelial cells, OAT1,OAT3protein expression decreased, URAT1protein and mRNA expression wassignificantly increased （P<0.01）. HE staining showed that the renal tissue of modelgroup rats showed focal interstitial fibrosis, glomerular atrophy and sclerosis part, another part of the renal tubular dilatation, see a small brown urate crystal deposition.Under the electron microscope morphological observation of mitochondrial cristae,matrix model group is shallow, proximal tubule cell chromatin condensation, hair sparse,degeneration of nucleus, cytoplasm and many lysosomes.Compared with the model group, after administration of total saponins of Dioscorea,high, medium, low dose group rats serum uric acid levels were significantlyreduced(μmol·L^-1,217.4±48.1,215.4±45.9,222.5±45.5vs276.5±68.0，P<0.01), uricacid clearance rate was significantly increased （P<0.01）, and urine volume were notsignificantly increased in rats; uric acid level,24h uric acid excretion increased, but nosignificant difference. Total saponins of Dioscorea high dose group rats serumcreatinine （Cr）, creatinine clearance rate, serum urea nitrogen （BUN） levels, serumXOD activity was significantly decreased （P<0.05⁰.01）. Renal proximal tubularepithelial cells, total saponins of Dioscorea high, middle dose group OAT1, OAT3protein expression increased significantly, significantly reduced the expression ofURAT1protein and mRNA （P<0.01）. HE staining showed that: the total saponins ofDioscorea high, middle dose group rare infiltration of interstitial fibrosis, accompaniedby a small amount of lymph and mononuclear cells, a small amount of glomerularatrophy, no hardening, the visible part of renal tubular epithelial cell edema, no browncrystal deposition. Low dose group showed a large number of interstitial fibrosis,accompanied by a large number of lymph and infiltration of mononuclear cells, a smallamount of glomerular atrophy, no hardening, massive edema of renal tubular epithelialcell degeneration. Under the electron microscope morphological observation of totalsaponins of Dioscorea high, middle dose group of proximal tubule structure better,mitochondria and cell bridge chain structure integrity, no degeneration of nucleus,vacuoles in cytoplasm, curved pipe and collagen fiber is lower than that of the normalgroup increased slightly, renal lesions were improved.Conclusion: the total saponins of Dioscorea can significantly decrease the level ofserum uric acid on hyperuricemia rats caused by adenine and ethambutol; its mechanism may be related to the down-regulation high expression of URAT1,up-regulation low expression of OAT1, OAT3is related to increase the excretion of uricacid,Inhibition of xanthine oxidase activity may also be one of its mechanisms.