Subchronic toxicity of ethylene glycol in Wistar and F-344 rats related to metabolism and clearance of metabolites.

Ethylene glycol (CAS RN 107-21-1) can cause kidney toxicity via the formation of calcium oxalate crystals in a variety of species, including humans. Numerous repeated dose studies conducted in rats have indicated that male rats are more susceptible than female rats. Furthermore, subchronic and chronic studies using different dietary exposure regimens have indicated that male Wistar rats may be more sensitive to renal toxicity than male Fischer-344 (F-344) rats. This study was conducted to compare the toxicity of ethylene glycol in the two strains of rats under identical exposure conditions and to evaluate the potential contribution of toxicokinetic differences to strain sensitivity. Ethylene glycol was mixed in the diet at concentrations to deliver constant target dosage levels of 0, 50, 150, 500, or 1000 mg/kg/day for 16 weeks to groups of 10 male Wistar and 10 male F-344 rats based on weekly group mean body weights and feed consumption. Kidneys were examined histologically for calcium oxalate crystals and pathology. Samples of blood, urine, and kidneys from satellite animals exposed to 0, 150, 500, or 1000 mg/kg/day for 1 or 16 weeks were analyzed for ethylene glycol, glycolic acid, and oxalic acid. Treatment of Wistar rats at 1000 mg/kg/day resulted in the death of two rats; in addition, at 500 and 1000 mg/kg/day, group mean body weights were decreased compared to control throughout the 16 weeks. In F-344 rats exposed at 1000 mg/kg/day and in Wistar rats receiving 500 and 1000 mg/kg/day, there were lower urine specific gravities, higher urine volumes, and increased absolute and relative kidney weights. In both strains of rats treated at 500 and 1000 mg/kg/day, some or all treated animals had increased calcium oxalate crystals in the kidney tubules and crystal nephropathy. The effect was more severe in Wistar rats than in F-344 rats. Accumulation of oxalic acid in the kidneys of both strains of rats was consistent with the dose-dependent and strain-dependent toxicity. As the nephrotoxicity progressed over the 16 weeks, the clearance of ethylene glycol and its metabolites decreased, exacerbating the toxicity. Benchmark dose analysis indicated a BMDL05 for kidney toxicity in Wistar rats of 71.5 mg/kg/day; nearly fourfold lower than in F-344 rats (285 mg/kg/day). This study confirms that the Wistar rat is more sensitive to ethylene glycol-induced renal toxicity than the F-344 rat and indicates that metabolism or clearance plays a role in the strain differences.     

Development of a physiologically based pharmacokinetic model for ethylene glycol and its metabolite, glycolic Acid, in rats and humans.

An extensive database on the toxicity and modes of action of ethylene glycol (EG) has been developed over the past several decades. Although renal toxicity has long been recognized as a potential outcome, in recent years developmental toxicity, an effect observed only in rats and mice, has become the subject of extensive research and regulatory reviews to establish guidelines for human exposures. The developmental toxicity of EG has been attributed to the intermediate metabolite, glycolic acid (GA), which can become a major metabolite when EG is administered to rats and mice at high doses and dose rates. Therefore, a physiologically based pharmacokinetic (PBPK) model was developed to integrate the extensive mode of action and pharmacokinetic data on EG and GA for use in developmental risk assessments. The resulting PBPK model includes inhalation, oral, dermal, intravenous, and subcutaneous routes of administration. Metabolism of EG and GA were described in the liver with elimination via the kidneys. Metabolic rate constants and partition coefficients for EG and GA were estimated from in vitro studies. Other biochemical constants were optimized from appropriate in vivo pharmacokinetic studies. Several controlled rat and human metabolism studies were used to validate the resulting PBPK model. When internal dose surrogates were compared in rats and humans over a broad range of exposures, it was concluded that humans are unlikely to achieve blood levels of GA that have been associated with developmental toxicity in rats following occupational or environmental exposures.     

Mode of action: oxalate crystal-induced renal tubule degeneration and glycolic acid-induced dysmorphogenesis--renal and developmental effects of ethylene glycol

Ethylene glycol can cause both renal and developmental toxicity, with metabolism playing a key role in the mode of action (MOA) for each form of toxicity. Renal toxicity is ascribed to the terminal metabolite oxalic acid, which precipitates in the kidney in the form of calcium oxalate crystals and is believed to cause physical damage to the renal tubules. The human relevance of the renal toxicity of ethylene glycol is indicated by the similarity between animals and humans of metabolic pathways, the observation of renal oxalate crystals in toxicity studies in experimental animals and human poisonings, and cases of human kidney and bladder stones related to dietary oxalates and oxalate precursors. High-dose gavage exposures to ethylene glycol also cause axial skeletal defects in rodents (but not rabbits), with the intermediary metabolite, glycolic acid, identified as the causative agent. However, the mechanism by which glycolic acid perturbs development has not been investigated sufficiently to develop a plausible hypothesis of mode of action, nor have any cases of ethylene glycol-induced developmental effects been reported in humans. Given this, and the variations in sensitivity between animal species in response, the relevance to humans of ethylene glycol-induced developmental toxicity in animals is unknown at this time.     

Mode of Action: Oxalate Crystal-Induced Renal Tubule Degeneration and Glycolic Acid-Induced Dysmorphogenesis—Renal and Developmental Effects of Ethylene Glycol

Ethylene glycol can cause both renal and developmental toxicity, with metabolism playing a key role in the mode of action (MOA) for each form of toxicity. Renal toxicity is ascribed to the terminal metabolite oxalic acid, which precipitates in the kidney in the form of calcium oxalate crystals and is believed to cause physical damage to the renal tubules. The human relevance of the renal toxicity of ethylene glycol is indicated by the similarity between animals and humans of metabolic pathways, the observation of renal oxalate crystals in toxicity studies in experimental animals and human poisonings, and cases of human kidney and bladder stones related to dietary oxalates and oxalate precursors. High-dose gavage exposures to ethylene glycol also cause axial skeletal defects in rodents (but not rabbits), with the intermediary metabolite, glycolic acid, identified as the causative agent. However, the mechanism by which glycolic acid perturbs development has not been investigated sufficiently to develop a plausible hypothesis of mode of action, nor have any cases of ethylene glycol-induced developmental effects been reported in humans. Given this, and the variations in sensitivity between animal species in response, the relevance to humans of ethylene glycol-induced developmental toxicity in animals is unknown at this time.     

连钱草提取物对肾结石模型大鼠的防治作用

目的观察连钱草提取物对肾结石模型大鼠的防治作用。方法大鼠饲饮含乙二醇和氯化铵的水建立肾结石模型,测定给药后各组大鼠24h排尿量,血清钙的含量,以及肾组织钙和草酸的含量。观察肾组织病理学变化。结果连钱草提取物可显著增加肾结石大鼠24h排尿量,明显降低肾组织草酸含量,以及血清和肾组织中钙含量,减少草酸钙结晶在肾组织中的沉积。结论连钱草提取物可以增加尿量,降低血清及肾组织中钙含量;减轻大鼠肾组织因结石引起的损伤和病变,减少’平内草酸钙结晶,从而防治肾结石。     

Incorporation of therapeutic interventions in physiologically based pharmacokinetic modeling of human clinical case reports of accidental or intentional overdosing with ethylene glycol.

Although occupational uses of the high production volume (HPV) chemical ethylene glycol (EG) have not been associated with adverse effects, there are case reports where humans have either intentionally or accidentally ingested large quantities of EG, primarily from antifreeze. The acute toxicity of EG can proceed through three stages, each associated with a different metabolite: central nervous system depression (ethylene glycol), cardiopulmonary effects associated with metabolic acidosis (glycolic acid), and ultimately renal toxicity (oxalic acid), depending on the total amounts consumed and the effectiveness of therapeutic interventions. A physiologically based pharmacokinetic (PBPK) model developed in a companion paper (Corley et al., 2005). Development of a physiologically based pharmacokinetic model for ethylene glycol and its metabolite, glycolic acid, in rats and humans. Toxicol. Sci., in press 2005) was refined in this study to include clinically relevant treatment regimens for EG poisoning such as hemodialysis or metabolic inhibition with either ethanol or fomepizole. Such modifications enabled the model to describe data from several human case reports, confirming the ability of the previous model to describe the pharmacokinetics of EG and its metabolite, glycolic acid, in humans across a broad range of doses and multiple exposure routes. By integrating the case report data sets with controlled studies in this PBPK model, it was demonstrated that fomepizole, if administered early enough in a clinical situation, can be more effective than ethanol or hemodialysis in preventing the metabolism of EG to more toxic metabolites. Hemodialysis remains an important option, however, if treatment is instituted after a significant amount of EG is metabolized or if renal toxicity has occurred.     

Effects of ethylene glycol and metabolites on in vitro development of rat embryos during organogenesis

The aim of this study was to investigate in vitro the relative impact of ethylene glycol, a major industrial chemical, and its individual metabolites on the embryonic development of rats. Rat whole embryos were exposed for 48 h (day 9.5–11.5 of gestation) to ethylene glycol (EG) and its metabolites glycolaldehyde (GAl), glycolic acid (GA), glyoxylic acid (GXA), glyoxale (GXAl) and oxalic acid (OXA) at increasing concentrations. Embryotoxic concentrations were achieved within the following range: ethylene glycol (100–200 m ), glycolic acid (3 m ), glyoxal (6 m ), oxalic acid (1–3 m ), glyoxylic acid (0.3–1 m ), glycolaldehyde (0.1–0.2 m ). The pattern of dysmorphogenesis with all compounds including EG showed a general embryotoxicity with diffusely distributed cell necroses with no specific target tissues selectively affected. The results obtained in this study emphasize the hypothesis that the metabolites and not ethylene glycol itself are responsible for the embryotoxicity of ethylene glycol in rats.     

Effect of Hygrophila spinosa in ethylene glycol induced nephrolithiasis in rats

Objective:

Hygrophila spinosa (Acanthaceae) is traditionally used to treat urinary calculi. The present study aimed to evaluate the antiurolithiatic activity of methanolic extract of Hygrophila spinosa (Acanthaceae) in ethylene glycol induced nephrolithiasic rats.

Materials and Methods:

Methanolic extract of Hygrophila spinosa (HSME) (250 and 500 mg/ kg body weight) was administered orally to male Wistar albino rats. Ethylene glycol (EG) was used to induce nephrolithiasis. The parameters studied included water intake, urinary volume, urinary pH, urinary and kidney oxalate and calcium, urinary magnesium and serum uric acid.

Results:

Ethylene glycol feeding resulted in hyperoxaluria as well as increased renal excretion of calcium and serum uric acid along with decreased excretion of urinary magnesium. Treatment with HSME significantly reduced the elevated urinary oxalate, urinary calcium and serum uric acid with increase in reduced urinary magnesium. Ethylene glycol feeding also resulted in increased levels of calcium and oxalate in kidney which was decreased after the treatment with HSME. The increased deposition of stone forming constituents in the kidneys of ethylene glycol treated rats was significantly lowered by treatment with HSME.

Conclusion:

The results indicate that the aerial parts of Hygrophila spinosa are endowed with antiurolithiatic activity, thereby justifying its traditional claim.KEY WORDS: Ethylene glycol, Hygrophila spinosa, kidney stones, nephrolithiasis     

Protective effect of the hydro-alcoholic extract of Rubia cordifolia roots against ethylene glycol induced urolithiasis in rats

This study investigated the protective effect of the hydro-alcoholic extract of roots of Rubia cordifolia Linn. (HARC) against ethylene glycol induced urolithiasis and its possible underlying mechanisms using male Wistar albino rats. Ethylene glycol feeding resulted in hyperoxaluria, hypocalciuria as well as increased renal excretion of phosphate. Supplementation with HARC significantly prevented change in urinary calcium, oxalate and phosphate excretion dose-dependently. The increased calcium and oxalate levels and number of calcium oxalate crystals deposits in the kidney tissue of calculogenic rats were significantly reverted by HARC treatment. The HARC supplementation also prevents the impairment of renal functions.     

Effect of A. lanata leaf extract and Vediuppu chunnam on the urinary risk factors of calcium oxalate urolithiasis during experimental hyperoxaluria.

Urolithiasis is one of the third most common afflictions found in humans. The efficacy of the two Siddha drugs, Aerva lanata and Vediuppu chunnam as antilithic agents using a urolithic rat model were tested in this study. Hyperoxaluria was induced in rats using 0.75% ethylene glycol in drinking water. Aerva lanata(3.0 mg kg(-1)body weight) and Vediuppu chunnam (3.5 mg kg(-1)body weight) were given orally for 28 days. Urinary risk factors of urolithiasis were monitored at the end of 7th, 14th, 21st and 28th days. Urinary volume was increased in hyperoxaluric as well as drug-treated rats. Increased urinary excretion of calcium, oxalate, uric acid, phosphorus and protein in hyperoxaluric rats was brought down significantly by the administration of A. lanata or Vediuppu chunnam. Decreased magnesium excretion in hyperoxaluric rats was normalized by drug treatment. The drug increases the urine volume, thereby reducing the solubility product with respect to calcium oxalate and other crystallizing salts such as uric acid, which may induce epitaxial deposition of calcium oxalate. Drug alone treated rats did not show any adverse effects. Combination therapy was found to be more effective and this indigenous medicine can be used successfully as an antilithic agent.     

Comparison of the metabolism of ethylene glycol and glycolic acid in vitro by precision-cut tissue slices from female rat, rabbit and human liver

1. The metabolism of [1,2-(14)C]-ethylene glycol and [1,2-(14)C]-glycolic acid was studied in vitro using precision-cut tissue slices prepared from the livers of female Sprague-Dawley rats, New Zealand white rabbits and humans. The time-course for production of metabolites formed from ethylene glycol at concentrations from 3 to 40 mM was determined to compare quantitatively the differences between species in the rates and amounts of formation of glycolic acid, the presumed developmental toxicant of ethylene glycol. The rates of metabolism of glycolic acid to glyoxylic acid at concentrations from 0.05 to 16 mM by liver tissue from the different species were also determined. The apparent V(max)/K(m) for the metabolic conversions of ethylene glycol to glycolic acid and for glycolic acid to glyoxylic acid in liver tissue from the different species were obtained. 2. There were qualitative differences in the metabolic profiles and quantitative differences in the formation of glycolic acid between the mammalian liver systems. There was an average of 10-fold less glycolic acid produced by liver slices from rabbits compared with rats. With the human liver, the formation of glycolic acid was not detectable using tissue from three of four human donors. A low level of glycolic acid was detected in one liver slice incubation from one of the four subjects, but only at one extended time point; glyoxylate was detected with liver slices from all four humans. 3. Liver slices prepared from female Sprague-Dawley rats, female New Zealand White rabbits and three female human subjects all metabolized glycolic acid to glyoxylic acid. Human liver tissue was the most effective at further metabolizing glycolic acid to glyoxylic acid. The ratios of V(max)/K(m), representing the relative clearance of glycolic acid from liver tissue, were approximately 14:9:1 for human, rat and rabbit liver, respectively. 4. Precision-cut liver slices maintained in dynamic organ culture are good predictors of metabolism by liver tissue in vivo. The results of the present study therefore indicate that levels of glycolic acid, if formed in vivo, following exposures to similar concentrations of ethylene glycol, would be lower in humans than in rabbits and rats.     

Ethylene glycol: an estimate of tolerable levels of exposure based on a review of animal and human data

Upon ingestion ethylene glycol (EG, monoethylene glycol) is rapidly absorbed from the gastrointestinal tract, and depending on the severity of exposure signs of toxicity may progress through three stages. Neurological effects characterize the first step consisting of central nervous depression (intoxication, lethargy, seizures, and coma). The second stage, usually 12–24 h after ingestion, is characterized by metabolic acidosis due to the accumulation of acidic metabolites of EG, primarily glycolic acid (GA), contributing to the ensuing osmolal and anion gaps. Stage 3, generally 24–72 h after ingestion, is determined mainly by oxalic acid excretion, nephropathy, and eventual renal failure. Because the toxicity of EG is mediated principally through its metabolites, adequate analytical methods are essential to provide the information necessary for diagnosis and therapeutic management. The severe metabolic acidosis and multiple organ failure caused by ingestion of high doses of EG is a medical emergency that usually requires immediate measures to support respiration, correct the electrolyte imbalance, and initiate hemodialysis. Since metabolic acidosis is not specific to EG, whenever EG intoxication is suspected, every effort should be made to determine EG as well as its major metabolite GA in plasma to confirm the diagnosis and to institute special treatment without delay. A number of specific and sensitive analytical methods (GC, GC-MS, or HPLC) are available for this purpose. Due to the rapid metabolism of EG, the plasma concentration of GA may be higher than that of EG already upon admission. As toxicity is largely a consequence of metabolism of EG to GA and oxalic acid, the simultaneous quantification of EG and GA is important. Formation of calcium oxalate monohydrate in the urine may be a useful indicator of developing oxalate nephrosis although urine crystals can result without renal injury. The pathways involved in the metabolism of EG are qualitatively similar in humans and laboratory animals, although quantitative differences have been reported. Comparison between species is difficult, however, because the information on humans is derived mainly from acute poisoning cases whereas the effects of repeated exposures have been investigated in animal experiments. Based on published data the minimum human lethal dose of EG has been estimated at approx. 100 ml for a 70-kg adult or 1.6 g/kg body weight (calculation of dose in ml/kg to mg/kg based in EG density=1.11 g/l). However, human data from case reports are generally insufficient for the determination of a clear dose-response relationship and quantification of threshold doses for systemic toxicity, in particular renal effects, is limited. As toxicity is largely a consequence of metabolism of EG to GA, it is important to note that no signs of renal injury have developed at initial plasma glycolate concentrations of up to 10.1 mM (76.7 mg/dl). Plasma EG levels of 3.2 mM (20 mg/dl) are considered the threshold of toxicity for systemic exposure, if therapeutic strategy is based on the EG concentration alone.     

The effect of partial hepatectomy on the toxicity of ethylene glycol, glycolic acid, glyoxylic acid and glycine

Glycine, glycolate, ethylene glycol and glyoxylate were force-fed to male rats on which partial hepatectomy had been performed. Urine was collected for 48 hr and assayed for oxalate and glyoxylate. Partial hepatectomy increased the toxicity of glyoxylate, decreased the toxicity of ethylene glycol and glycolate, and increased the urinary oxalate of rats fed glyoxylate, but not of rats fed ethylene glycol, glycine and glycolate. Liver regeneration was not altered by the oxalate precursors employed. [U-¹⁴C]Glycine, [U-¹⁴C]ethylene glycol, [U-¹⁴C]-glycolate, and [U-¹⁴C]glyoxylate were oxidized to [U-¹⁴C]oxalate by the isolated perfused liver. The order for increased oxalate synthesis was glycine, ethylene glycol, glycolate and glyoxylate. The results suggest that the toxicity of ethylene glycol and glycolate is due to the formation of metabolic products such as glyoxylate or oxalate. The liver was identified as the major source of endogenous oxalate synthesis in the rat.     

The cytotoxicity of oxalate, metabolite of ethylene glycol, is due to calcium oxalate monohydrate formation

Oxalate is a minor, but important metabolite of ethylene glycol and has been directly linked with acute and subchronic renal toxicity in ethylene glycol poisoning. Numerous studies have characterized the cytotoxicity of oxalate as including plasma membrane damage and organelle injury. Oxalate has two forms in vivo: oxalate ions and calcium oxalate monohydrate (COM) crystals that readily form in the presence of calcium. The present study was designed to compare the cytotoxicity of the oxalate ion and COM crystals in human and rat cells. In rat red blood cells, the oxalate ion did not increase hemolysis, while COM crystals produced hemolysis with a concentration-dependent increase. In human proximal tubule (HPT) cells in culture, COM suspensions, at concentrations >3 mM but with no oxalate ion, caused cytotoxicity as evidenced by the release of lactate dehydrogenase (LDH) into media. Cytotoxicity was not observed in HPT cells treated with oxalate solutions that contained no COM because EDTA prevented its formation. The cytotoxic effects of COM to HPT cells were potentiated by acidosis (pH 6.5), but not by glycolate, the major metabolite of ethylene glycol. The toxicity of COM to HPT cells and to proximal tubule cells from Wistar and F-344 rats, compared using both ethidium homodimer uptake and LDH leakage, increased in human and rat cells in a concentration-dependent manner. Rat cells were more sensitive to COM than HPT cells, but there were no apparent differences between the effects in Wistar cells and F-344 cells. These results demonstrate that COM crystals, and not the oxalate ion, are responsible for the membrane damage and cell death observed in normal human and rat PT cells and suggest that COM accumulation in the kidney is responsible for the renal toxicity associated with ethylene glycol exposure.     

Antilithiatic Effect of Melia azedarach. on Ethylene Glycol–Induced Nephrolithiasis in Rats

Abstract

The effect of the aqueous extract of Melia azedarach. Linn. (Meliaceae) against ethylene glycol–induced nephrolithiasis in male Wistar albino rats is summarized in this study. Lithiasis was induced in rats by administering 0.75% ethylene glycol in drinking water for 28 days and was manifested by high urinary calcium, phosphate, oxalate, and low urinary magnesium content. Simultaneous administration of aqueous extract of Melia azedarach. (AEMA; 250 mg/kg body weight) orally for 28 days along with ethylene glycol (0.75%) reduced urinary calcium, oxalate, phosphate, and elevated urinary magnesium level. It also increased the urine volume, thereby reducing the tendency for crystallization. The histopathological studies confirmed the induction of lithiasis as microcrystal deposition was observed in sections of kidney from animals treated with ethylene glycol. This was reduced, however, after treatment with the extract. These observations enable us to conclude that AEMA is effective against ethylene glycol–induced nephrolithiasis.     

Ethylene glycol induced renal toxicity in female Wistar rats

The calcium oxalate nephrolithiasis due to ethylene glycol treatment has long been observed in male species but the prevalence of calcium oxalate nephrolithiasis in female species due to ethylene glycol has been still a subject of controversy. Ethylene glycol was administered in drinking water at three different doses (0.4%, 0.75% and 1.0%, v/v) for 28 days in female Wistar rats. Ethylene glycol treatment caused significant decrease in body weight and corresponding increase in relative organ weight with significant hypercalciuria, hyperoxaluria and proteinuria as well as increased retention of calcium, oxalate, phosphate and total protein in kidney in a dose — and time — dependent manner. However, calcium level was significantly reduced in the serum while an increase in total protein and phosphate level in serum was observed. Furthermore, there was a significant reduction in magnesium level in urine, serum and kidney due to ethylene glycol. The effects were also confirmed in histopathological studies.     

Comparison of the metabolism of ethylene glycol and glycolic acid in vitro by precision-cut tissue slices from female rat,rabbit and human liver

1.?The metabolism of [1,2-¹⁴C]-ethylene glycol and [1,2-¹⁴C]-glycolic acid was studied in vitro using precision-cut tissue slices prepared from the livers of female Sprague—Dawley rats, New Zealand white rabbits and humans. The time-course for production of metabolites formed from ethylene glycol at concentrations from 3 to 40 mM was determined to compare quantitatively the differences between species in the rates and amounts of formation of glycolic acid, the presumed developmental toxicant of ethylene glycol. The rates of metabolism of glycolic acid to glyoxylic acid at concentrations from 0.05 to 16 mM by liver tissue from the different species were also determined. The apparent V_maJK_m for the metabolic conversions of ethylene glycol to glycolic acid and for glycolic acid to glyoxylic acid in liver tissue from the different species were obtained.

2.?There were qualitative differences in the metabolic profiles and quantitative differences in the formation of glycolic acid between the mammalian liver systems. There was an average of 10-fold less glycolic acid produced by liver slices from rabbits compared with rats. With the human liver, the formation of glycolic acid was not detectable using tissue from three of four human donors. A low level of glycolic acid was detected in one liver slice incubation from one of the four subjects, but only at one extended time point; glyoxylate was detected with liver slices from all four humans.

3.?Liver slices prepared from female Sprague—Dawley rats, female New Zealand White rabbits and three female human subjects all metabolized glycolic acid to glyoxylic acid. Human liver tissue was the most effective at further metabolizing glycolic acid to glyoxylic acid. The ratios of F"_max/-/C_m, representing the relative clearance of glycolic acid from liver tissue, were approximately 14:9:1 for human, rat and rabbit liver, respectively.

4.?Precision-cut liver slices maintained in dynamic organ culture are good predictors of metabolism by liver tissue in vivo. The results of the present study therefore indicate that levels of glycolic acid, if formed in vivo, following exposures to similar concentrationsof ethylene glycol, would be lower in humans than in rabbits and rats.     

Alcea rosea root extract as a preventive and curative agent in ethylene glycol-induced urolithiasis in rats

Introduction:

Alcea rosea L. is used in Asian folk medicine as a remedy for a wide range of ailments. The aim of the present study was to investigate the effect of hydroalcoholic extract of Alcea rosea roots on ethylene glycol-induced kidney calculi in rats.

Materials and Methods:

Male Wistar rats were randomly divided into control, ethylene glycol (EG), curative and preventive groups. Control group received tap drinking water for 28 days. Ethylene glycol (EG), curative and preventive groups received 1% ethylene glycol for induction of calcium oxalate (CaOx) calculus formation; preventive and curative subjects also received the hydroalcoholic extract of Alcea rosea roots in drinking water at dose of 170 mg/kg, since day 0 or day 14, respectively. Urinary oxalate concentration was measured by spectrophotometer on days 0, 14 and 28. On day 28, the kidneys were removed and examined histopathologically under light microscopy for counting the calcium oxalate deposits in 50 microscopic fields.

Results:

In both preventive and curative protocols, treatment of rats with hydroalcoholic extract of Alcea rosea roots significantly reduced the number of kidney calcium oxalate deposits compared to ethylene glycol group. Administration of Alcea rosea extract also reduced the elevated urinary oxalate due to ethylene glycol.

Conclusion:

Alcea rosea showed a beneficial effect in preventing and eliminating calcium oxalate deposition in the rat kidney. This effect is possibly due to diuretic and anti-inflammatory effects or presence of mucilaginous polysaccharides in the plant. It may also be related to lowering of urinary concentration of stone-forming constituents.KEY WORDS: Alcea rosea, malvaceae, kidney calculi, ethylene glycol, calcium oxalate     

Antiurolithic effect of berberine is mediated through multiple pathways

Berberine is an isoquinoline alkaloid, occurring in nature as the main constituent of several plants with medicinal use in kidney stone disease. This work was undertaken to evaluate its antiurolithic potential and explore the possible underlying mechanism(s). Berberine was tested in vitro for the antioxidant effect and in vivo for diuretic and antiurolithic effects on an animal model of calcium oxalate urolithiasis. Berberine exhibited concentration-dependent (50-150μg/ml) antioxidant effect against ferrous-ascorbate induced lipid peroxidation in rat kidney homogenate with potency slightly higher than the reference antioxidant, butylated hydroxytoluene. In Wistar rats, berberine (5-20mg/kg) increased urine output accompanied by increased pH and Na(+) and K(+) excretion and decreased Ca(2+) excretion, similar to hydrochlorothiazide. In an animal model of calcium oxalate urolithiasis developed in male Wistar rats by adding 0.75% ethylene glycol in drinking water, berberine (10mg/kg) prevented as well as eliminated calcium oxalate crystal deposition in renal tubules and protected against deleterious effects of lithogenic treatment including weight loss, impaired renal function and oxidative stress, manifested as increased malondialdehyde and protein carbonyl contents, depleted GSH and decreased antioxidant enzyme activities of the kidneys. In na?ve rats, berberine (10mg/kg) increased urine volume and pH and decreased Ca(2+) excretion. Results of this study suggest the presence of antiurolithic effects in berberine against calcium oxalate stones mediated through a combination of antioxidant, diuretic, urinary alkalinizing and hypocalciuric effects. These data invite future studies on berberine to establish its efficacy for clinical use.     

The effect of dietary refined sugars and sugar alcohols on renal calcium oxalate deposition in ethylene glycol-treated rats

The effect of administering refined carbohydrates in the diet on calcium oxalate deposition in the kidneys of rats given 1% (v/v) ethylene glycol in their drinking-water was investigated. The rats were given 0, 2.5, 10, 30 or 60% sucrose in the feed (w/w) and/or drinking-water (w/v) or 20% (w/w) starch, glucose, sucrose, fructose, galactose, xylitol or sorbitol in the feed for 3 wk. All of the animals remained healthy over the test period as far as could be assessed by the measurement of 19 plasma biochemical parameters. The inclusion of 30 or 60% (w/w) sucrose in the diet resulted in a more than tenfold increase in the deposition of calcium oxalate in the kidneys. However, this deposition could not be predicted from data on urinary pH and urinary excretion of calcium, oxalate and urate, which have been reported to be risk factors for stone formation. There was no evidence of increased rates of oxalate production from ethylene glycol. The administration of fructose, xylitol or sorbitol was associated with the greatest renal deposition of calcium oxalate, and glucose was associated with by far the least.