Testosterone Enhances whereas Estrogen Inhibits Calcium Oxalate Stone Formation in Ethylene Glycol Treated Rats

Purpose

The present study was conducted to extend our earlier study on the role of testosterone in the pathogenesis of urolithiasis and to further investigate the influence of sex hormone on the pathogenesis of calcium oxalate stone.

Materials and Methods

Adult Sprague-Dawley rats were divided into 9 groups, each containing 10 rats. Two groups of rats were left untreated and served as male and female controls. Another 7 groups of rats were fed a 0.5 percent ethylene glycol (EG) lithogenic diet for 4 weeks. Among them, 2 groups were male and female rats, 2 groups were castrated, 2 groups were castrated and then were subcutaneously implanted with testosterone, and 1 group of intact female rats was also subcutaneously implanted with testosterone. The stone and crystal deposits were examined by infrared spectrometer and polarizing and scanning electron microscope, respectively. Serum testosterone, creatinine and electrolytes and the renal excretion of oxalate, citrate and creatinine were determined.

Results

Subcutaneous implantation of exogenous testosterone restored calcium oxalate stone formation in castrated, EG-treated male rats (80 percent) and enhanced urolithiasis in castrated female rats receiving EG (40 percent). However, the testosterone effect was less striking in intact female rats fed EG (10 percent).

Conclusions

These data suggest that testosterone can promote and estrogen may inhibit calcium oxalate stone formation in EG-treated rats.     

The influence of sex hormones on renal osteopontin expression and urinary constituents in experimental urolithiasis

PURPOSE: To our knowledge the influence of sex hormones on urinary stone formation remains undetermined. We investigated the effect of castration on urinary lithogenic factors and renal osteopontin expression in rats previously treated with ethylene glycol. MATERIALS AND METHODS: Sprague-Dawley rats were divided normal males, castrated males, males with 2 weeks of 0.75% ethylene glycol treatment, castrated males with 2 weeks of 0.75% ethylene glycol treatment, normal females, castrated females, females with 2 weeks of 0.75% ethylene glycol treatment and castrated females with 2 weeks of 0.75% ethylene glycol treatment. We analyzed 24-hour urine samples for urinary constituents, such as calcium, oxalate, citrate, uric acid, phosphate, magnesium, sodium, potassium and creatinine. The kidneys were examined for osteopontin expression by Northern blot analysis and for crystal deposition by histological examination. RESULTS: In intact male rats calcium and citrate excretion decreased and oxalate excretion increased significantly after ethylene glycol treatment. Castrated male rats with ethylene glycol had greater calcium and less oxalate excretion than male intact rats with ethylene glycol. In intact female rats uric acid excretion decreased and only calcium excretion increased significantly after ethylene glycol treatment. Castrated female rats with ethylene glycol excreted significantly more oxalate and less calcium than intact female rats with ethylene glycol. Renal osteopontin expression was the same in male intact and castrated rats, and in female intact and castrated rats. In males with ethylene glycol expression was stronger in castrated than in intact rats. In females with ethylene glycol expression was weaker in castrated than in intact rats. No crystal deposits were found in the kidneys in any group. CONCLUSIONS: Testosterone appears to promote stone formation by suppressing osteopontin expression in the kidneys and increasing urinary oxalate excretion. Estrogen appears to inhibit stone formation by increasing osteopontin expression in the kidneys and decreasing urinary oxalate excretion.     

鱼油抑制实验鼠草酸钙结晶形成

目的 了解鱼油在尿石形成中的作用。方法 ６０只大鼠随机分４组,饮用１％乙二醇（ＥＧ）水,同时喂饲不同剂量的鱼油。４周后检测各组大鼠肾功能、草酸钙结晶、２４小时尿钙和尿草酸。结果 加服鱼油组鼠肾积水、组织水肿减轻,肾组织内草酸钙结晶数及含钙量明显减少,２４小时尿钙排出减少;尿尿素氮、肌酐排出明显增加,而血中尿素氮、肌酐浓度显著低于成石组。结论 鱼油能抑制实验性高草酸尿症大鼠体内草酸钙结晶形成,减少尿     

Vitamin E therapy prevents hyperoxaluria-induced calcium oxalate crystal deposition in the kidney by improving renal tissue antioxidant status

OBJECTIVE: To determine whether vitamin E prevents hyperoxaluria-induced stone formation, using a new animal model of calcium oxalate stone disease, as our previous in- vitro and in-vivo studies showed that oxalate and hyperoxaluria induce free-radical generation, which results in peroxidative injury to renal tubular cells. MATERIALS AND METHODS: Ethylene glycol (EG) was administered at 150 mg/day by gavage for 3 weeks to rats fed on diets with adequate (group 1), excess (group 2) or deficient (group 3) vitamin E. Several indicators of peroxidation, free radicals and enzymatic activity were then assessed. RESULTS: EG treatment in group 1 lead to increased lipid peroxidation, protein thiol, excretion of urinary enzymes, oxalate and decreases in urinary calcium, antioxidant enzymes and altered glutathione redox balance. Although renal function was not altered, there was increased water intake, urine volume and lowered urinary pH in these rats. These changes were more intense, with extensive calcium-oxalate crystal deposition, in rats in group 3, and prevented in rats in group 2, except for urinary oxalate levels, which remained high. Histopathological examination showed that there was no deposition of calcium oxalate crystals in rats in group 2. CONCLUSION: This is the first study to demonstrate in-vivo evidence that hyperoxaluria-induced peroxidative injury induces individual calcium oxalate crystal attachment in the renal tubules. In addition, excess vitamin E completely prevented calcium oxalate deposition, by preventing peroxidative injury and restoring renal tissue antioxidants and glutathione redox balance. Therefore, vitamin E therapy might provide protection against the deposition of calcium oxalate stones in the kidney of humans.     

Antioxidant therapy prevents ethylene glycol-induced renal calcium oxalate crystal deposition in Wistar rats

Purpose

Renal epithelial cell injury by reactive oxygen species is a prerequisite step in the pathogenesis of urolithiasis, and there is increasing evidence that reactive oxygen species is produced and oxidative stress (OS) is developed during idiopathic calcium oxalate nephrolithiasis. It appears that the administration of natural antioxidants has been used to protect against nephrolithiasis in human and experimental animals.

Methods

Calcium oxalate urolithiasis was induced experimentally by administration of 0.75 % v/v ethylene glycol in drinking water of male Wistar rats weighing 150–200 g. Study was conducted in 4- and 8-week periods. In the 4-week period, Group 1 (control) was fed a standard commercial diet. Group 2 received the same diet with the addition of 0.75 % of ethylene glycol (EG). Group 3 received EG plus the diet, and water with additional antioxidant nutrients, and lemon juice as the dietary source of citrate (EG + AX). Group 4 was the same as Group 3, but with no EG in water. In the 8-week study protocol, Group 5 was fed the standard diet with EG in water for the first 28 days, followed with no EG. Group 6 (curative group) received the diet with EG for the first 28 days, followed by discontinuation of EG plus the addition of antioxidant nutrients. Group 7 was provided the diet with antioxidant nutrients for 8 weeks. Group 8 (preventive group) received the diet with antioxidant nutrients for 4 weeks, followed by antioxidant nutrients with EG for the next 4 weeks. Lime juice was given along the antioxidants. After treatment period, kidneys were removed and used for histopathological examination.

Results

In the 4-week study, the mean number of crystal deposits in Group 2 was significantly higher than that of animals in Group 3. After 8 weeks, animals given curative antioxidant supplementation within the second 4-week period developed fewer deposits in Group 6 as compared to Group 5 animals. In the other preventive AX loading Group 8, the number of crystal deposits was substantially less than that of either Group 2 or Group 5 animals (EG-treated rats).

Conclusion

Results showed a beneficial effect on treating and superior renal protection for preventing stone deposition in the rat kidney. These results provide a scientific rationale for preventive and treatment roles of antioxidant nutrient complex in human kidney stone disease.     

Effect of magnesium on calcium oxalate urolithiasis

Previous studies have shown that hypomagnesuria induced by magnesium deficient diet causes calcium oxalate crystal deposition in renal tubules of hyperoxaluric rats and administration of magnesium to these rats results in prevention of calcium oxalate crystallization in their kidneys. Based on these studies magnesium was claimed to be beneficial for calcium oxalate stone patients. However, hypomagnesuria is not a common phenomenon. To better understand the role of magnesium as an inhibitor of calcium oxalate crystallization in urine, we studied the effect of magnesium on calcium oxalate urolithiasis in rats on a regular diet and a hyperoxaluric protocol. Excess magnesium was administered to male rats on regular diet and a lithogenic protocol. Magnesium administration to hyperoxaluric rats did not result in significant changes in urinary excretion of calcium or oxalate or in calcium oxalate relative supersaturation. Urinary excretion of citrate was also not significantly altered. Some animals from both groups, those on magnesium therapy and those not on magnesium therapy had crystals deposited in their renal tubules. We conclude that excess magnesium has no significant effect on calcium oxalate urolithiasis in normomagnesuric conditions.     

Ethylene glycol induces calcium oxalate crystal deposition in Malpighian tubules: a Drosophila model for nephrolithiasis/urolithiasis

Several animal species are used to study calcium oxalate urolithiasis; however, an ideal model has yet to be identified. We used Drosophila as a model organism and fed the flies lithogenic agents such as ethylene glycol, hydroxyl-L-proline, and sodium oxalate. At different times, the Malpighian tubules, the kidney equivalent of insects, were dissected and a polarized light microscope used to highlight the birefringent crystals. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed that the crystal composition was predominately calcium oxalate. Furthermore, administration of potassium citrate successfully reduced the quantity of and modulated the integrity of the ethylene glycol-induced crystals. Thus, the Drosophila model of bio-mineralization produces crystals in the urinary system through many lithogenic agents, permits observation of crystal formation, and is amenable to genetic manipulation. This model may mimic the etiology and clinical manifestations of calcium oxalate stone formation and aid in identification of the genetic basis of this disease.     

Dietary oxalate and calcium oxalate nephrolithiasis

PURPOSE: Patients with calcium oxalate kidney stones are advised to decrease the consumption of foods that contain oxalate. We hypothesized that a cutback in dietary oxalate would lead to a decrease in the urinary excretion of oxalate and decreased stone recurrence. We tested the hypothesis in an animal model of calcium oxalate nephrolithiasis. MATERIALS AND METHODS: Hydroxy-L-proline (5%), a precursor of oxalate found in collagenous foods, was given with rat chow to male Sprague-Dawley rats. After 42 days rats in group 1 continued on hydroxy-L-proline, while those in group 2 were given chow without added hydroxy-L-proline for the next 21 days. Food and water consumption as well as weight were monitored regularly. Once weekly urine was collected and analyzed for creatinine, calcium, oxalate, lactate dehydrogenase, 8-isoprostane and H(2)O(2). Urinary pH and crystalluria were monitored. Rats were sacrificed at 28, 42 and 63 days, respectively. Renal tissue was examined for crystal deposition by light microscopy. RESULTS: Rats receiving hydroxy-L-proline showed hyperoxaluria, calcium oxalate crystalluria and nephrolithiasis, and by day 42 all contained renal calcium oxalate crystal deposits. Urinary excretion of lactate dehydrogenase, 8-isoprostane and H(2)O(2) increased significantly. After hydroxy-L-proline was discontinued in group 2 there was a significant decrease in urinary oxalate, 8-isoprostane and H(2)O(2). Half of the group 2 rats appeared to be crystal-free. CONCLUSIONS: Dietary sources of oxalate can induce hyperoxaluria and crystal deposition in the kidneys with associated degradation in renal biology. Eliminating oxalate from the diet decreases not only urinary oxalate, but also calcium oxalate crystal deposits in the kidneys and improves their function.     

雄激素对结石诱导雄鼠肾内结晶体的影响

目的探讨雌激素对尿石症患者的影响。方法用0．5％乙二醇诱导结石形成，建立4组动物实验雄鼠模型。A组：去势结石组；B组：去势 皮下注射睾丸酮（3mg／d）结石组;C组：结石对照组；D组；正常对照组（标准无结石饮食）。4组雄鼠饲养4周后同时宰杀，分别测定和比较他们血清Testo、FSH、LH、E2、PRL、Prog，肾内晶体沉和部位及程度。结果A、B、C各组间差异均有显著性（P＜O．001）。结论雄性激素对尿石症有一定影响。     

Effects of urinary pH and acid-base balance on the formation of calcium oxalate stone

The effects of urinary pH and acid-base balance on the calcium oxalate stone formation was investigated by two experiments. 24-hr urine samples were collected from 15 recurrent CaOx stone formers, 9 single stone formers and 6 age-matched controls. Inhibitory effect of 1% urine in various pH (4.0-9.0) were calculated by a seed crystal method. In the seed crystal system, there were no significant differences in the inhibitory activity of aggregation (Ia) and in the inhibitory activity of size (Is) for each pH of metastable solution between the stone former group and the control group. However, the value of Ia and Is showed a tendency of rise in proportion to a rise in pH. Rats model for calcium oxalate urolithiasis were fed with three different diets (1% NH4Cl, 5% NaHCO3 and 8% NaHCO3 diet) for three weeks. On the fourth week, 24-hr urine samples were collected. In the animal experiment, calcium oxalate stone formations were predominantly recognized in the kidney of the 1% NH4Cl diet group. The biochemical data showed an increase of urinary calcium and oxalate, and a decrease of urinary citrate. These results suggest that low urinary pH and metabolic acidosis are promoters of the calcium oxalate stone formation.     

月见草油抑制草酸钙结晶形成的实验研究

目的了解月见草油在草酸钙结石形成中的作用,为临床治疗提供新的方法与思路。方法雄性SD大鼠60只,随机分为4组,各组15只。C组和D组以月见草油（含γ-亚麻酸9.2%）或葵花籽油（含亚油酸70%）10g/kg灌胃4周后,用诱石剂1%乙二醇（EG）加2%氯化氨喂饮,同时继续以月见草油或葵花籽油灌胃4周,8周后检测各组大鼠肾功能、24h血尿生化指标和肾草酸钙结晶情况;仅饲普通饲料（A组,空白组）和普通饲料加1%乙二醇（EG）加2%氯化氨喂饮（B组,成石组）大鼠作为对照。结果月见草油组肾组织水肿较轻,肾内草酸钙结晶数及肾成石率低于成石组（P〈0.05）,尿枸橼酸较成石组高（P〈0.01）,24h尿钙、尿草酸排泄均低于成石组（P〈0.01）,血尿素氮（P〈0.01）、血肌酐（P〈0.05）低于成石组。结论γ-亚麻酸能有效改善肾功能,减少尿钙及草酸的排泄,抑制实验鼠肾草酸钙结晶形成,在尿石症防治方面可能有一定应用价值。     

Inhibitory effects of female sex hormones on urinary stone formation in rats.

BACKGROUND: The effects of female sex hormones on urinary stone formation are not known. This study was conducted to investigate the effects of these hormones on stone formation by using an ethylene glycol (EG) and vitamin D-induced rat urolithiasis model. METHODS: Adult female Wistar rats were fed the same diet for four weeks and were then divided into four groups (N = 10 each). One group was administered 0.5 ml of olive oil three times per week for four weeks as a control. The other three groups were administered 0. 5 microg of vitamin D3 and 0.5 ml of 5% EG three times per week for four weeks. The rats in two of these three groups were oophorectomized, and the rats of the remaining group underwent a sham operation on the day before the start of the four-week treatment period. One of the two oophorectomized groups was then administered a supplementation of female sex hormones (0.1 mg of estrogen and 2.5 mg of progesterone 3 times per week for 4 weeks). On the first day of the fifth week of the experimental period, the degree of crystal deposition was determined histologically, and the calcium content in renal tissue was measured. We also investigated the level of osteopontin (OPN) mRNA in renal tissues by Northern blot analysis. OPN is a matrix protein thought to be a promoter of stone formation. RESULTS: The urinary oxalate excretion, crystal deposition and calcium content in renal tissue and the expression of OPN-mRNA were greater in the oophorectomized rats compared with the controls, and the same parameters were inhibited by the female sex hormone supplementation. CONCLUSIONS: These results suggest that female sex hormones can inhibit renal crystal deposition in EG-treated rats by suppressing the urinary oxalate excretion and the expression of OPN.     

Calcium oxalate crystal localization and osteopontin immunostaining in genetic hypercalciuric stone-forming rats

BACKGROUND: The inbred genetic hypercalciuric stone-forming (GHS) rats develop calcium phosphate (apatite) stones when fed a normal 1.2% calcium diet. The addition of 1% hydroxyproline to this diet does not alter the type of stone formed, while rats fed this diet with 3% hydroxyproline form mixed apatite and calcium oxalate stones and those with 5% hydroxyproline added form only calcium oxalate stones. The present study was designed to determine the localization of stone formation and if this solid phase resulted in pathologic changes to the kidneys. METHODS: GHS rats were fed 15 g of the standard diet or the diet supplemented with 1%, 3%, or 5% hydroxyproline for 18 weeks. A separate group of Sprague-Dawley rats (the parental strain of the GHS rats), fed the standard diet for a similar duration, served as an additional control. At 18 weeks, all kidneys were perfusion-fixed for structural analysis, detection of crystal deposits using the Yasue silver substitution method, and osteopontin immunostaining. RESULTS: There were no crystal deposits found in the kidneys of Sprague-Dawley rats. Crystal deposits were found in the kidneys of all GHS rats and this Yasue-stained material was detected only in the urinary space. No crystal deposits were noted within the cortical or medullary segments of the nephron and there was no evidence for tubular damage in any group. The only pathologic changes occurred in 3% and 5% hydroxyproline groups with the 5% group showing the most severe changes. In these rats, which form only calcium oxalate stones, focal sites along the urothelial lining of the papilla and fornix of the urinary space demonstrated a proliferative response characterized by increased density of urothelial cells that surrounded the crystal deposits. At the fornix, some crystals were lodged within the interstitium, deep to the proliferative urothelium. There was increased osteopontin immunostaining in the proliferating urothelium. CONCLUSION: Thus in the GHS rat, the initial stone formation occurred solely in the urinary space. Tubular damage was not observed with either apatite or calcium oxalate stones. The apatite stones do not appear to cause any pathological change while those rats forming calcium oxalate stones have a proliferative response of the urothelium, with increased osteopontin immunostaining, around the crystal deposits in the fornix.     

Determinant role of testosterone in the pathogenesis of urolithiasis in rats.

By using an ethylene glycol-induced urolithiasis model, we assessed the role of testosterone in the pathogenesis of urolithiasis. The intact and castrated male and female rats were fed with 0.5% ethylene glycol in drinking water for four weeks. The renal excretions of oxalate, citrate and other electrolytes were measured, and the stone and crystal deposit were examined microscopically. The results showed that drinking a loading of 0.5% ethylene glycol for four weeks produced hyperoxaluria in all rats, but the intact male rats excreted more urinary oxalate than any other groups of rats. The ethylene glycol-fed rats exhibited hypocitraturia except the castrated male rats. However, urolithiasis occurred in intact male but not female rats. Castration in male rats fed with ethylene glycol dramatically decreased the incidence of renal stone from 71.4% (5/7) to 14.3% (1/7). On the other hand, there was still no renal stone formed in the oophorectomized female rats which received ethylene glycol treatment. These data indicate that serum testosterone level plays a determinant role in urolithiasis formation.     

Effect of high-calcium diet on urinary oxalate excretion in urinary stone formers

The effect of mild high-calcium diet or regular-calcium diet on urinary calcium excretion, urinary oxalate excretion, urinary calcium/creatinine ratio, urinary oxalate/creatinine ratio, and the probability of being a stone former (PSF) were studied in 85 patients with idiopathic urolithiasis. Intake of high-calcium diet for 5-6 days reduced (p less than 0.01-p less than 0.001) urinary oxalate excretion, urinary oxalate/creatine ratio and PSF in patients with idiopathic hypercalciuria. Under the regular-calcium diet, administration of 60 mg/day of pyridoxal phosphate for 3 months lowered (p less than 0.05-p less than 0.01) urinary oxalate excretion, urinary oxalate/creatinine ratio and PSF in patients with idiopathic hypercalciuria alone. From these findings, intake of mild high-calcium diet appears to be beneficial to decrease the urinary oxalate excretion and PSF in patients with idiopathic hypercalciuria. Pyridoxal phosphate has all the features of suppressing such risk factors for stone formation in patients with idiopathic hypercalciuria.     

肾结石大鼠肾组织bikunin mRNA的表达

目的 :研究bikunin在实验性肾草酸钙结石大鼠肾组织的表达及意义。方法 :采用乙二醇和氯化铵诱导大鼠肾草酸钙结石模型形成 ,检测各组大鼠肾功能、肾组织Ca2 + 含量和草酸钙晶体沉积、尿生化指标 ,并用逆转录聚合酶链反应 (RT PCR)检测bikuninmRNA在肾组织的表达情况。结果 :模型组大鼠的血清Cr、BUN、肾Ca2 + 含量、2 4h尿Ca2 + 、草酸 (Ox)分泌量和肾组织bikuninmRNA的表达均明显高于正常组 (P <0 .0 5 )。结论 :高草酸尿和草酸钙结晶的沉积能促使大鼠肾脏通过合成更多的bikunin来抑制大鼠肾组织草酸钙晶体的形成。     

Preventive effects of green tea on renal stone formation and the role of oxidative stress in nephrolithiasis

PURPOSE: Urinary stones are similar to arteriosclerosis in epidemiology, mechanism, calcification composition and age at frequent occurrence. The calcification that occurs in arteriosclerosis is inhibited by antioxidants. Green tea leaves contain approximately 13% catechins, which have been shown to have antioxidant effects. We investigated the inhibitory, antioxidative effects of green tea on calcium urinary stone formation. MATERIALS AND METHODS: A total of 120 Wistar rats were divided into 4 groups, namely group 1-control rats receiving saline, group 2-stone group rats administered ethylene glycol (EG) and vitamin D3, group 3-drink group rats administered EG, vitamin D3 and green tea given as drinking water, and group 4-powder group rats administered EG, vitamin D3 and 2.5% powdered green tea leaves mixed in a powder diet. Pooled 24-hour urine samples and blood samples were collected and the 2 kidneys were excised 7, 14 and 21 days after administration, respectively. One kidney was used for immunohistological examination of osteopontin, superoxide dismutase (SOD), p65, p53 and bcl-2 expression, in situ hybridization of osteopontin and detection of apoptosis, while the other was used for quantitative analysis of SOD activity. RESULTS: Green tea treatment decreased urinary oxalate excretion and calcium oxalate deposit formation. Green tea treatment increased SOD activity compared with the stone group. The degree of apoptosis in the stone group was significantly increased compared with the drink and powder groups. CONCLUSIONS: The inhibitory effect of green tea on calcium oxalate urolithiasis is most likely due to antioxidative effects.     

钙敏感受体活性改变对大鼠泌尿系草酸钙结石形成的影响

目的探讨钙敏感受体（CaSR）活性改变对草酸钙结石形成的影响。方法在实验期间给予乙二醇和氯化铵诱导雄性SD大鼠产生泌尿系草酸钙结石。在造模期间给予不同剂量的CaSR抑制剂（NPS-2390）。实验结束时检测各组大鼠血尿素氮（BUN）、肌酐（Cr）、血磷、血钙、血镁、PTH的含量、24h尿量、尿pH值、尿钙、镁、尿草酸的分泌量,显微镜下观察肾组织切片中草酸钙结晶沉积及病理变化情况及肾脏中CaSR表达情况。从而评价CaSR活性的改变对泌尿系结石形成的影响。结果成石对照组大鼠血BUN、Cr、尿草酸、尿钙较空白组明显升高并且有大量结晶形成,表明建模成功。CaSR抑制剂组较成石对照组甲状旁腺激素（PTH）的分泌增加并且血Ca2＋升高尿钙升高。肾组织病理学检查显示CaSR抑制组的肾脏组织中的草酸钙结晶较成石对照组明显增加,组织病理损伤也较重。结论肾脏中及甲状旁腺中CaSR的表达下降可以导致草酸钙结晶的形成增加。     

Urine composition following jejunoileal bypass

The urinary excretion of oxalate, calcium, citrate, magnesium, urate and creatinine and the inhibition of calcium oxalate crystal growth were determined in 30 patients operated with three different types of jejunoileal bypass. In addition the ion-activity products of calcium oxalate and calcium oxalate saturation were calculated. 15 of the patients had formed urolithiasis postoperatively. The patients were investigated on an out-patient basis with their ordinary diet. All patients had hyperoxaluria. The oxalate excretion did not seem to decrease with time after operation. The patients operated with a biliointestinal shunt had a significantly higher excretion of oxalate than those with the other two types of operation, indicating that variations in the anatomy of the small intestine after jejunoileal bypass might result in different absorption of oxalate or oxalate precursors. Urinary oxalate, calcium oxalate saturation and ion-activity products were higher whereas the excretion of calcium, magnesium and citrate was lower in patients than in controls. The urine volumes, excretion of creatinine and urate and inhibition of calcium oxalate crystal growth were equal in patients and controls. Analogous urine composition was found in patients both with and without urolithiasis with the exception of a higher magnesium excretion observed in stone formers.     

Lemon juice has protective activity in a rat urolithiasis model

Background

The use of herbal medicines (medicinal plants or phytotherapy) has recently gained popularity in Europe and the United States. Nevertheless the exact mechanism of the preventive effects of these products is still far to be clearly established, being its knowledge necessary to successfully apply these therapies to avoid stone formation.

Methods

The effect of oral lemon juice administration on calcium oxalate urolithiasis was studied in male Wistar rats. Rats were rendered nephrolithic by providing drinking water containing 0.75% ethylene glycol [v/v] (EG) and 2% ammonium chloride [w/v] (AC) for 10 days. In addition to EG/AC treatment, three groups of rats were also gavage-administered solutions containing 100%, 75% or 50% lemon juice [v/v] (6 μl solution/g body weight). Positive control rats were treated with EG/AC but not lemon juice. Negative control rats were provided with normal drinking water, and were administered normal water by gavage. Each group contained 6 rats. After 10 days, serum samples were collected for analysis, the left kidney was removed and assessed for calcium levels using flame spectroscopy, and the right kidney was sectioned for histopathological analysis using light microscopy.

Results

Analysis showed that the rats treated with EG/AC alone had higher amounts of calcium in the kidneys compared to negative control rats. This EG/AC-induced increase in kidney calcium levels was inhibited by the administration of lemon juice. Histology showed that rats treated with EG/AC alone had large deposits of calcium oxalate crystals in all parts of the kidney, and that such deposits were not present in rats also treated with either 100% or 75% lemon juice.

Conclusion

These data suggest that lemon juice has a protective activity against urolithiasis.