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.     

Prechronic Toxicity Studies on 2-Ethylhexanol in F334 Rats and B6C3F1 Mice

Data on the subchronic toxicity of 2-ethylhexanol (2EH) wererequired to establish the dose vehicle and dose levels for oncogenicitystudies. In preliminary studies 2EH was given subacutely (11days) to male and female Fischer 344 rats and B6C3F1 mice asan aqueous emulsion by oral gavage (0, 100, 330, 1000, and 1500mg/kg/day). Clinical observations were made, body weights, foodconsumption, clinical chemistries, hematologies, and selectedorgan weights were measured, and gross and micropathologieswere performed. Target organs were the central nervous system,liver, forestomach, spleen, thymus, and kidney in rats and thecentral nervous system, liver, and forestomach in mice. 2EHwas then administered by oral gavage to male and female F344rats and B6C3F1 mice as an aqueous emulsion (0, 25, 125, 250,and 500 mg/kg/day) for 13 weeks. At 500 mg/kg/day in the ratthere was reduced body weight gain (6% male, 7% female), increasedrelative liver (29% male, 15% female), kidney (16% male, 6%female), stomach (11% male, 16% female), and testes (6%) weights,and moderate gross and microscopic changes in the liver andforestomach. There were no behavioral effects or effects onthe spleen or thymus. A no-effect level for target organ effectsin the rat was 125 mg of 2EH/kg/day. At 500 mg of 2EH/kg/dayin the mouse the only effects were increased relative stomachweights in males (13%) and a low incidence of gross and microscopicfindings in the forestomach (male and female) and liver (female).A no-effect level for target organ effects in the mouse was125 mg of 2EH/kg/day. 2EH was a peroxisome proliferator in therat but not in the mouse at subchronic dose levels of 500 mg/kg/day.Dose levels in oncogenicity studies were set at 50 mg/kg/dayfor the absence of treatment-related effects in rats and mice,and 500 and 750 mg/kg/day, respectively, in rats and mice ashigh doses producing minimal toxicity without altering the lifespan.     

Extension of a PBPK model for ethylene glycol and glycolic acid to include the competitive formation and clearance of metabolites associated with kidney toxicity in rats and humans

A previously developed PBPK model for ethylene glycol and glycolic acid was extended to include glyoxylic acid, oxalic acid, and the precipitation of calcium oxalate that is associated with kidney toxicity in rats and humans. The development and evaluation of the PBPK model was based upon previously published pharmacokinetic studies coupled with measured blood and tissue partition coefficients and rates of in vitro metabolism of glyoxylic acid to oxalic acid, glycine and other metabolites using primary hepatocytes isolated from male Wistar rats and humans. Precipitation of oxalic acid with calcium in the kidneys was assumed to occur only at concentrations exceeding the thermodynamic solubility product for calcium oxalate. This solubility product can be affected by local concentrations of calcium and other ions that are expressed in the model using an ion activity product estimated from toxicity studies such that calcium oxalate precipitation would be minimal at dietary exposures below the NOAEL for kidney toxicity in the sensitive male Wistar rat. The resulting integrated PBPK predicts that bolus oral or dietary exposures to ethylene glycol would result in typically 1.4-1.6-fold higher peak oxalate levels and 1.6-2-fold higher AUC's for calcium oxalate in kidneys of humans as compared with comparably exposed male Wistar rats over a dose range of 1-1000 mg/kg. The converse (male Wistar rats predicted to have greater oxalate levels in the kidneys than humans) was found for inhalation exposures although no accumulation of calcium oxalate is predicted to occur until exposures are well in excess of the theoretical saturated vapor concentration of 200 mg/m³. While the current model is capable of such cross-species, dose, and route-of-exposure comparisons, it also highlights several areas of potential research that will improve confidence in such predictions, especially at low doses relevant for most human exposures.     

Developmental Toxicity Evaluation of Ethylene Glycol by Gavage in New Zealand White Rabbits

Artificially inseminated New Zealand white (NZW) rabbits wereadministered ethylene glycol (EG) by gavage on Gestational Days(GD) 6 through 19 at doses of 0, 100, 500, 1000, or 2000 mg/kg/day,with 23–24 inseminated animals per group. Clinical signswere recorded and water consumption was measured daily; doeswere weighed on GD 0, 6–19, 25, and 30. At necropsy (GD30), maternal liver, kidney, and gravid uterine weights wererecorded. Histopathologic examination was performed on kidneysfrom 10 does/dose and for all unscheduled deaths. Ovarian corporalutea were counted and uterine implantation sites (total sites,resorptions, dead and live fetuses) were recorded. All livefetuses were weighed, sexed, and examined for external, visceral,and skeletal malformations and variations. EG resulted in profoundmaternal toxicity at 2000 mg/kg/day (42% mortality; three earlydeliveries and one spontaneous abortion) associated with renalpathology and unaccompanied by any other indicators of maternaltoxicity. Renal lesions at 2000 mg/kg/day involved the corticalrenal tubules and included intraluminal oxalate crystals, epithelialnecrosis, and tubular dilatation and degeneration. No dose-relatedmaternal toxicity occurred at 100–1000 mg/kg/day. Therewas no indication of developmental toxicity at any dose tested,including no effects on pre- or postimplantation loss, numberof fetuses, fetal body weight, or sex ratio (% male fetuses)per litter, and no evidence of teratogenicity. The "no observableadverse effect level" (NOAEL) for maternal toxicity was therefore1000 mg/kg/day and the NOAEL for developmental toxicity wasat least 2000 mg/kg/day in this study. The sensitivity of NZWrabbits relative to that of Sprague—Dawley rats and Swissmice for maternal and developmental toxicity from gavage administrationof EG during organogenesis can be determined for maternal toxicity:rabbits>mice>rats, and for developmental toxicity, mice>>rats >> rabbits.     

Determination of a No-Observed-Effect Level for Developmental Toxicity of Ethylene Glycol Administered by Gavage to CD Rats and CD-1 Mice

Previous studies have indicated that ethylene glycol (EG) isa developmental toxicant in rats and mice primarily when ingested.This study was designed to establish no-observed-effect levels(NOELs) for developmental toxicity of EG administered by gavagein both rodent species. Dams were administered EG on GestationDays 6–15; rats were given 0, 150, 500, 1000, or 2500mg EG/kg/ day; mice were dosed with 0, 50, 150, 500, or 1500mg EG/kg/day. In rat dams given 2500 mg EG/kg/day, water consumptionwas increased during treatment and body weights were reducedthroughout gestation; liver and kidney weights were increasedat euthanization (Gestation Day 21). Relative liver weightswere also increased at 1000 mg/kg/day. Effects observed in ratfetuses at 2500 mg/kg/day included the following hydrocephaly;gastroschisis; umbilical hernia; fused, duplicated, or missingarches, centra, and ribs; poor ossification in thoracic andlumbar regions; and reduced body weights. Reduced body weights,duplicated or missing ribs, centra, and arches, and poor ossificationwere also ob served in rat fetuses at 1000 mg/kg/day. In mice,there was no apparent treatment-related maternal toxicity. Inmouse fetuses (Gestation Day 18), effects were observed at 1500mg/kg/day and included reduced body weights, fused ribs andarches, poor ossification in thoracic and lumbar centra, andincreased occurrence of an extra 14th rib. At 500 mg/kg/day,slight reductions in fetal body weight and increased incidencesof extra ribs were observed. Under conditions of these studies,NOELs for developmental toxicity were 500 mg/kg/day for ratsand 150 mg/kg/day for mice, indicating that mice were more susceptiblethan rats to the teratogenic effects of EG.     

Subacute and subchronic toxicity of ethylene glycol administered in drinking water to Sprague-Dawley rats

Subacute (10-day) and subchronic (90-day) toxicity studies of ethylene glycol (EG) were conducted in male and female Sprague-Dawley rats to provide the U.S. Environmental Protection Agency's (EPA) Office of Drinking Water with toxicity data for final preparation of a Health Advisory for the chemical. Ethylene glycol was administered in drinking water at concentrations of 0.5, 1.0, 2.0, and 4.0% for both sexes in the 10-day study. Based on a projected consumption rate of 100 ml/kg/day, the respective doses on a mg/kg/day basis would be 554, 1108, 2216, and 4432. These dose levels were also used in the 90-day study for females, but dose levels for the males in the 90-day study were 0.25, 0.5, 1.0, and 2.0% (227, 554, 1108, and 2216 mg/kg/day). At time of sacrifice necropsies were performed and tissues were prepared for histological evaluation. Blood samples were taken for hematology and clinical chemistry determinations. Body weights were measured weekly. Water and food consumption were determined three times weekly. No mortality occurred in the 10-day study. In the 90-day study 8/10 females and 2/10 males in the high dose group died prior to sacrifice. Body weights were suppressed in a dose response fashion for males and females. Hemoglobin, hematocrit, erythrocytes, and leukocytes were all significantly decreased in female rats receiving 4% EG for 10 days. The most significant histopathological findings, seen predominantly in males, were kidney lesions which included calcium oxalate crystals in tubules and pelvic epithelium; tubular dilation and degeneration; intratubular proteinaceous material; and inflammation in tubules and pelvic epithelium. At the same dose of ethylene glycol, males had more kidney lesions and much higher incidence and severity of lesions than the females.     

Effects of megadoses of pyridoxine on spermatogenesis and male reproductive organs in rats

Although it has been indicated that many neurotoxicants also cause reproductive toxicity, the reproductive toxicity of megadoses of pyridoxine, which is a neurotoxicant, has not been studied. In this paper, we studied the effects of megadoses of pyridoxine on male reproductive organs. Pyridoxine hydrochloride, 125 mg/kg, 250 mg/kg, 500 mg/kg or 1000 mg/kg, daily, was intraperitoneally injected into Wistar male rats 5 days a week for 2 or 6 weeks, and its effects on the male reproductive organs were investigated. After 2 weeks of administration, absolute weights of the testis in the 500 and 1000 mg/kg epididymis in all the exposed groups and prostate gland in the 1000 mg/kg group decreased, and mature spermatid counts in the testis decreased in the 1000 mg/kg group. After 6 weeks administration, the absolute and relative weights of the testis, epididymis, prostate gland and seminal vesicle decreased in the 500 mg/kg and 1000 mg/kg groups, and mature spermatid counts in the testis and sperm counts in the epididymis decreased in these groups. Among the marker enzymes of the testicular cells, LDH-X activity decreased, and -glucuronidase activity, cytochrome P-450 content and cytochrome b5 content increased in the 1000 mg/kg group. Plasma testosterone concentration did not significantly alter in all the exposed groups. From these results, it was concluded that megadoses of pyridoxine affected the spermatogenesis and decreased reproductive organ weights in the rat.     

Percutaneous toxicity of ethylene glycol monomethyl ether and of dipropylene glycol monomethyl ether in the rat

The subacute percutaneous toxicity of dipropylene glycol monomethyl ether (DPM) in male rats dosed 5 days/week for 4 weeks under both occluded and unoccluded conditions has been assessed and compared to the percutaneous toxicity of ethylene glycol monomethyl ether (EGM). DPM caused no significant changes in the clinical chemistry, haematology, or pathology, whereas EGM caused changes in the haematology and clinical chemistry, and both testicular and bone marrow damage at doses of 1000 mg/kg per day.     

Repeated dose toxicity and developmental toxicity of diisopropanolamine to rats.

The repeated dose oral and dermal toxicity of diisopropanolamine (DIPA) was evaluated in rats and compared to the reported toxicity of the related secondary alcohol amine, diethanolamine (DEA). Fischer 344/DuCrl rats were given up to 750 mg/kg/day by dermal application, 5 days/week, for 4 weeks; or up to 1,000 mg DIPA/kg/day by drinking water for 13 weeks to evaluate potential toxic effects. Time-mated female CRL:CD(SD) rats were given up to 1,000 mg/kg/day by gavage on gestation days (GD) 6-20 for evaluation of maternal and fetal effects. In the dermal toxicity study, no adverse treatment-related in-life effects other than mild irritation at the site of dermal application at >or= 500 mg/kg/day were observed. There were no systemic effects in rats given up to 750 mg/kg/day. In the subchronic oral toxicity study, the most significant effects were an increase in absolute and relative kidney weights, unaccompanied by histopathologic changes, at >or= 500 mg/kg/day DIPA. The latter effect was ameliorated following a 4-week recovery period. In the developmental toxicity study, there were no maternal or developmental effects at any dose level evaluated. The toxicity of DIPA contrasts with that of DEA which has been shown to affect a number of organ systems when repeatedly administered orally or dermally at similar or lower dosages.     

Reproductive toxicity studies in rats with rimexolone, a corticoid ophthalmic suspension.

Rimexolone is a potent anti-inflammatory corticosteroid with a lower potential for elevating intraocular pressure, relative to other ophthalmic steroids, and is indicated for postsurgical inflammation and uveitis. Fertility and peri/postnatal toxicities were evaluated at oral gavage doses of 50, 150 or 500 mg/kg, and developmental toxicity at 100, 500, or 1000 mg/kg. In the fertility study, male rats were treated daily beginning 4 weeks prior to mating and females were treated daily beginning 2 weeks prior to mating, and through gestation day 6. Females were necropsied on gestation day 15 and males were necropsied after 10 weeks of exposure. In males, dose-related reductions in mean body weights, body weight gains, and food consumption occurred in all groups. In the 500 mg/kg females, mean body weights were reduced during gestation, and there was an increase in early resorptions and concomitant decrease in viable fetuses at this level. There were no effects on copulation or fertility indices, or on the number of corpora lutea and implantation sites. The no-observed-effect level (NOEL) for fertility and reproductive effects was 150 mg/kg. In the developmental toxicity study, female rats were treated daily from gestation days 6 through 17, necropsied on gestation day 20 and fetuses were evaluated. Maternal toxicity occurred at 500 and 1000 mg/kg as indicated by reduced maternal body weights and body weight gains. However, there was no indication of a developmental effect on fetuses due to rimexolone. The NOEL was 1000 mg/kg for the developing fetuses. In the peri/postnatal toxicity study, female rats were treated daily from gestation day 6 through lactation day 20 and necropsied. F1 developmental and behavioral parameters were evaluated. Selected F1 animals were mated at 12 weeks, allowed to deliver, and necropsied on lactation day 21. At 500 mg/kg, F0 maternal body weights were reduced during gestation and lactation, and F1 pup weights were reduced during lactation and the growth phase. There were no effects on the F1 fertility or reproductive capabilities, or on F2 developmental parameters. The NOEL for the F0 females and F1 offspring was 150 mg/kg. Together, these studies indicate that, unlike some corticosteroids, rimexolone does not produce developmental or reproductive toxicity in rats.     

Comparative toxicity of ethylene dichloride in F344/N, Sprague-Dawley and Osborne-Mendel rats

Studies were conducted to compare the toxicity of ethylene dichloride (EDC) in F344/N rats, Sprague-Dawley rats, and Osborne-Mendel rats. Ten rats/sex/group were exposed to EDC in drinking-water at 0, 500, 1000, 2000, 4000 and 8000 ppm for 13 wk. The highest concentration was limited by the maximum solubility of EDC in water (about 9000 ppm). In addition, F344/N rats (10/sex/group) were administered EDC in corn oil by gavage to compare toxicity resulting from bolus administration with that of continuous exposure in drinking-water. Gavage doses of EDC were within the range of total daily doses (in mg/kg body weight/day) resulting from exposure in drinking-water. EDC administered by gavage resulted in greater toxicity to F344/N rats than did administration of similar doses in drinking-water. All males receiving 240 and 480 mg/kg body weight and 9/10 females receiving 300 mg/kg body weight by gavage died before the end of the study. Necrosis of the cerebellum was observed in the brains of 3 males receiving 240 mg/kg body weight and 3 females receiving 300 mg/kg body weight. Hyperplasia and inflammation of the forestomach mucosa were observed in 8 male and 3 female rats that died or were killed in moribund condition. EDC caused minimal toxicity to F344/N, Sprague-Dawley and Osborne-Mendel rats at the drinking-water concentrations used in these studies; only female F344/N rats had EDC-related renal lesions. Based on mortality and EDC-related lesions, the no-effect levels for EDC administered by gavage to F344/N rats were 120 mg/kg body weight for males and 150 mg/kg body weight for females.     

One-generation reproductive toxicity study of 2-methylbutane in Sprague-Dawley rats

This study investigated the potential reproductive toxicity of 2-methylbutane in a one-generation reproductive toxicity study using Sprague-Dawley rats. A total of 24 male and female rats per group were given 2-methylbutane by gavage at 0, 100, 300, and 1000 mg/kg/day. Males were dosed for 10 weeks prior to mating and during mating. Females were dosed from 2 weeks before mating to day 21 of lactation. At 1000 mg/kg/day, both genders exhibited an increase in adrenal gland weight, however, a decrease in body weight gain and food intake, an increase in kidney weight, and an increased incidence of histopathological changes of the kidney were also observed in male rats. No treatment-related effects of 2-methylbutane were found in relation to the reproductive capacity of parental animals or the pre- and post-natal development of the F1 generation. There were no treatment-related effects in either gender at ≤ 300 mg/kg/day. Under these experimental conditions, the no-observed-adverse-effect level of 2-methylbutane was 300 mg/kg/day for general toxicity and 1000 mg/kg/day for reproductive capacity and pup development in rats.     

Subchronic oral toxicity, tissue distribution and clearance of hexachloroethane in the rat

Hexachloroethane (HCE) was fed to Fischer 344 rats at approximate doses of 0, 1, 15 or 62 mg/kg/day for 16 weeks. Selected tissues were assayed at termination for HCE content. Histopathological examination identified the kidney as the primary target organ with male rats more sensitive than female rats. The kidney concentration of HCE increased proportionately with dose in the males, but there were disproportionately small increases with dose in females. A group of male rats was given 62 mg/kg/day for 8 weeks to estimate tissue clearance. Clearance of HCE from fat, liver, kidney and blood occurred in an apparent first-order manner with a half-life of approximately 2.5 days. The apparent first-order elimination suggests that HCE metabolism and excretion were not saturated in rats given up to 62 mg/kg/day and suggests that, in the range of doses given, toxicity should be proportional to exposure concentration. The no-observable-effect level (NOEL) for toxicity was 1 mg/kg/day for male and female rats.     

Effects of valproic acid on fertility and reproductive organs in male rats

Crj:CD(SD)IGS rats were orally administered valproic acid at doses of 250, 500 or 1000 mg/kg/day for 4, 7 or 10 weeks. At each dose, one group of male rats was euthanized after 4-week dosage (4-week dose group) and the other two were mated with untreated females after 4 (7-week dose group) or 7 (10-week dose group) weeks of treatment with valproic acid and their fertility was evaluated. Females were euthanized on day 14-17 of gestation, and numbers of corpora lutea, implantations and live and dead fetuses were recorded. After 4, 7 or 10 weeks of treatment, males were euthanized, genital organs were weighed, the number of sperm in the cauda epididymis was counted, sperm motion analyzed, and histopathological examination of testes performed. The male rats of the 1000 mg/kg dose group died or were moribund 3 or 4 days after the start of treatment. No effects on fertility of male rats were observed up to the 500 mg/kg 10-week dose group. Treatment for 4 weeks at 500 mg/kg/day decreased epididymis weight. After 7 weeks at 500 mg/kg/day, the weights of epididymis, seminal vesicles and prostate were decreased, and the number of sperm heads per cauda epididymis and percentage of motile sperm were reduced. In the 500 mg/kg 10-week dose group, the weight of testis was decreased. On histopathological examination of the testis, degeneration of seminiferous tubules and loss or exfoliation of spermatids were observed, and the ratio of retention of step 19 spermatids in stage IX-XI was increased in the 500 mg/kg 4-, 7- and 10-week dose groups. These results suggest that analysis of sperm motion and histopathological evaluation of testes are sensitive methods for assessing toxicity of valproic acid on male reproductive organs.     

Developmental toxicity study with diethylene glycol dosed by gavage to CD rats and CD-1 mice.

Diethylene glycol (DEG; CAS Number 111-46-6) is a widely used industrial liquid chemical with a potential for human exposure. In view of the established teratogenic effects caused by ethylene glycol in laboratory animals, the developmental toxicity of DEG was investigated in mice and rats, species known to be sensitive to the developmental toxicity of ethylene glycol. Timed-pregnant CD-1 mice and CD rats were dosed daily by gavage with undiluted DEG over gestational days (gd) 6-15. Based on probe studies, mouse dosages were 0 (distilled water), 559, 2795 and 11,180 mg/kg/day, and those for rats 0, 1118, 4472 and 8944 mg/kg/day. They were examined daily for clinical signs of toxicity, and body weights, food consumption and water consumption measured periodically throughout gestation. At necropsy, on gd 18 (mice) or gd 21 (rats), dams were examined for gross pathology and body, gravid uterus, liver and kidney weights were measured. Maternal rat kidneys were examined histologically. Fetuses were weighed, sex determined, and examined for external, visceral and skeletal variations and malformations. With mice there was maternal toxicity at 11,180 mg/kg/day (mortality, signs, increased water consumption) and at 2795 mg/kg/day (increased water consumption). Implantations were comparable across all groups. Fetal body weights were significantly reduced at 11,180 mg/kg/day. There were no increases in variations or malformations, either total, by category, or individually. With rats, maternal toxicity was present at 8944 mg/kg/day (mortality, signs, reduced body weight gain, reduced food consumption, increased water consumption, increased liver weight, increased kidney weight, and renal histopathology), and 4472 mg/kg/day (increased water consumption). There were no treatment-related effects on corpora lutea or implantations. Fetal body weights were reduced at 8944 mg/kg/day. There were no significant effects with respect to total or individual external or visceral variations. Individual skeletal variations were significantly increased at 8944 mg/kg/day (poorly ossified interparietal, poorly ossified thoracic centra number 10 and number 13, and bilobed thoracic centrum number 10) and 4472 mg/kg/day (split anterior arch of atlas and bilobed thoracic centrum number 10). This pattern of delayed ossification is consistent with reduced fetal body weight. Malformations, total, by category, or individually, were similar between the control and DEG groups. Thus, under the conditions of these studies, the no-observed-effect-level (NOEL) for DEG given by gavage over gd 6-15 was 559 mg/kg/day with the mouse and 1118 mg/kg/day with the rat for maternal toxicity, and 2795 mg/kg/day with mice and 1118 mg/kg/day with rats for developmental toxicity (fetotoxicity). There were no indications of embryotoxicity or teratogenic effects at any dosage in either species.     

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.     

Subchronic Oral Toxicity,Tissue Distribution and Clearance of Hexachloroethane in the Rat

ABSTRACT

Hexachloroethane (HCE) was fed to Fischer 344 rats at approximate doses of 0, 1, 15 or 62 mg/kg/day for 16 weeks. Selected tissues were assayed at termination for HCE content. Histopathological examination identified the kidney as the primary target organ with male rats more sensitive than female rats. The kidney concentration of HCE increased proportionately with dose in the males, but there were disproportionately small increases with dose in females. A group of male rats was given 62 mg/kg/day for 8 weeks to estimate tissue clearance. Clearance of HCE from fat, liver, kidney and blood occurred in an apparent first-order manner with a half-life of approximately 2.5 days. The apparent first-order elimination suggests that HCE metabolism and excretion were not saturated in rats given up to 62 mg/kg/day and suggests that, in the range of doses given, toxicity should be proportional to exposure concentration. The no-observable-effect level (NOEL) for toxicity was 1 mg/kg/day for male and female rats.     

Potential estrogenic and antiestrogenic activity of the cyclic siloxane octamethylcyclotetrasiloxane (D4) and the linear siloxane hexamethyldisiloxane (HMDS) in immature rats using the uterotrophic assay.

The cyclic siloxane octamethylcyclotetrasiloxane (D4) and the linear siloxane hexamethyldisiloxane (HMDS) have numerous industrial and consumer applications and thus have the potential for human exposure. The present study was undertaken to examine potential estrogenic and antiestrogenic activities of D4 and HMDS. To address potential differences in sensitivity between rat strains the study used both Sprague-Dawley (SD) and Fischer 344 (F-344) rats. Estrogenicity of the test compounds was determined by measuring absolute and relative uterine weights in immature rats and by monitoring uterine epithelial cell height. In order to place the data obtained for D4 into perspective relative to strong and weak estrogenic compounds, the response produced by D4 at 0, 10, 50, 100, 250, 500, and 1000 mg/kg/day was compared to responses produced by ethinyl estradiol (EE) (1, 3, 10, or 30 microg/kg/day), diethylstilbestrol dipropionate (DES-DP) (0.5, 1.5, 5, 15 microg/kg/day), and coumestrol (CE) (10, 35, 75, 150 mg/kg/day). Antiestrogenic effects were evaluated by co-administering D4 (500 mg/kg/day) with EE at 1, 3, 10, and 30 microg /kg/day. All compounds were administered in sesame oil at a volume of 5 mL/kg by oral gavage. Beginning on postnatal day 18 (SD) or 21 (F-344) each pup (12 per group) received a single dose of test compound once a day for 4 consecutive days. The pups were euthanized the morning after the last treatment and their uteri removed, weighed, and processed for histological examination. EE and DES-DP produced a significant dose-dependent increase in absolute and relative uterine weights and uterine cell height. The maximum increase in uterine weight following EE exposure was approximately 350% relative to controls in both strains. The weak phytoestrogen CE also produced a dose-related increase in absolute and relative uterine weight and epithelial cell height, but the response occurred over a much higher range of doses. At the highest dose of CE, uterine weight was increased approximately 230% relative to controls. Following exposure to D4, absolute and relative uterine weights and uterine epithelial cell height were statistically significantly increased in both strains of rats at doses above 100 mg/kg/day. In terms of uterine weight, D4 was approximately 0.6 million times less potent than EE or DES-DP in SD pups and 3.8 million times less potent than EE or DES-DP in F-344 pups. The maximal increase in uterine weight, relative to controls, produced by D4 at 1000 mg/kg/day was approximately 160% in SD rats, while the maximum increase produced by D4 in F-344 rats was 86%. D4 co-administered over a wide range of EE doses, resulted in a significant reduction in uterine weight compared to EE alone. HMDS was evaluated in SD rats only. The response produced by HMDS (600 and 1200 mg/kg/day) was compared to EE (3 microg/kg/day). Antiestrogenic effects were evaluated by co-administering HMDS (1200 mg/kg/day) with EE at 3 microg/kg/day. HMDS had no measurable effect on uterine weight under the experimental conditions described here. However, HMDS coadministered with EE did produce a small, but statistically significant reduction in uterine weight compared to EE alone. In conclusion, D4 showed weak estrogenic and antiestrogenic activity that was several orders of magnitude less potent than EE, and many times less potent than the weak phytoestrogen CE.     

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.     

Testicular toxicity of dietarily or parenterally administered bisphenol A in rats and mice.

Male Crj:Wistar rats, HsdHot:Holtzman SD rats, Crj:CD-1(ICR) mice and C57BL/6CrSlc mice were administered bisphenol A (BPA) in the diet at a level of 0 (control) and 0.25% for 8 weeks. Daily BPA intake was about 200 and 400 mg/kg for rats and mice, respectively. No conspicuous signs of general or reproductive toxicity were observed after administration in any strain of these animals. Serum testosterone concentrations were not decreased in BPA-fed rats and mice. Successive subcutaneous administration of BPA at a dose of 200 mg/kg/day for 4 weeks significantly decreased the testis, epididymis, prostate and seminal vesicle weights, and the testicular daily sperm production in Jcl:Wistar rats. Successive intraperitoneal administration of BPA at a dose of 20 mg/kg/day for 4 weeks decreased the prostate and seminal vesicle weights but not the testis or epididymis weights. An intraperitoneal dose of 2 mg BPA/kg/day did not cause any toxicity. These results indicate that dietarily administered BPA is less toxic to most strains of rats and mice, and the maximum non-toxic dose and/or minimum toxic dose may be about 200 mg/kg/day. Subcutaneous or intraperitoneal BPA is much more toxic on male reproductive and sex accessory organs than dietary.