Renal function tests as indicators of kidney injury in subacute toxicity studies

Combustion-Derived Pollutants Linked with Kidney Disease in Low-Lying Flood-Affected Areas in the Balkans

Tens of thousands of people in southern Europe suffer from Balkan endemic nephropathy (BEN), and four times as many are at risk. Incidental ingestion of aristolochic acids (AAs), stemming from the ubiquitousAristolochia clematitis(birthwort) weed in the region, leads to DNA adduct-induced toxicity in kidney cells, the primary cause of BEN. Numerous cofactors, including toxic organics and metals, have been investigated, but all have shown small contributions to the overall BEN relative to non-BEN village distribution gradients. Here, we reveal that combustion-derived pollutants from wood and coal burning in Serbia also contaminate arable soil and test as plausible causative factors of BEN. Using a GC-MS screening method, biomass-burning-derived furfural and coal-burning-derived medium-chain alkanes were detected in soil samples from BEN endemic areas levels at up to 63-times and 14-times higher, respectively, than in nonendemic areas. Significantly higher amounts were also detected in colocated wheat grains. Coexposure studies with cultured kidney cells showed that these pollutants enhance DNA adduct formation by AA, - the cause of AA nephrotoxicity and carcinogenicity. With the coincidence of birthwort-derived AAs and the widespread practice of biomass and coal burning for household cooking and heating purposes and agricultural burning in rural low-lying flood-affected areas in the Balkans, these results implicate combustion-derived pollutants in promoting the development of BEN.

Glutathione conjugation and protein modification resulting from metabolic activation of pesticide metalaxyl in vitro and in vivo

Metalaxyl (MTL), a germicidal agent, is widely used in agriculture. Due to the biological amplification effect, MTL entering the ecological environment would result in a threat to human health through the food chain. MTL is reportedly accumulated in liver. The objectives of the study included investigating the metabolic activation of MTL in liver and defining the mechanisms participating in the hepatotoxicity of MTL. The corresponding glutathione (GSH), N-acetylcysteine (NAC) conjugate, and cysteine conjugates were observed in liver microsomes, prepared from liver tissues of mice, containing MTL and GSH, NAC or cysteine. These conjugates were also detected in urine and bile of rats receiving MTL. Apparently, MTL was biotransformed to a quinone imine intermediate dose-dependently attacking the thiols and cysteine residues of protein. The bioactivation of MTL required cytochrome P450 enzymes, and CYP3A dominated the bio-activation of MTL.

Evaluation of the acute and 28-day sub-acute intravenous toxicity of α-l-guluronic acid (ALG; G2013) in mice

α-l-Guluronic acid (ALG; G2013) has been previously introduced as a new anti-inflammatory agent with promising therapeutic effects. Thus, in the present study, we aimed to evaluate the acute and sub-acute toxicity of ALG through intravenous (i.v.) administration in Balb/C mice. ALG was administrated i.v. to the mice with doses of 300, 600, and 1000 mg/kg of body weight to investigate acute toxicity (single dose) and with doses of 25, 50, and 100 mg/kg of body weight to sub-acute toxicity study (daily injections for a period of 28 days). The mortality rate, food and water intake, behavior, body weight, gross necropsy, hematological and biochemical parameters as well as histopathological presentations of the vital organs (kidneys, liver, lungs, spleen, and heart) were examined in treated groups and compared to the healthy controls. The results of both acute and sub-acute studies showed that i.v. administrations of ALG did not affect the investigated parameters in both sexes, indicating that the LD₅₀ of ALG was higher than 1000 mg/kg of body weight. As no difference was observed in toxicity profiles of investigated doses, no-observed-adverse-effect-level for i.v. administration of ALG in the sub-acute study was greater than 100 mg/kg body weight in both female and male mice. According to the finding, i.v. administration of ALG did not lead to any clinical sign in abovementioned doses, suggesting that ALG was well tolerated up to 1000 mg/kg. These pre-clinical findings support the application of ALG in the future clinical trials.

Sub-chronic toxicity evaluation of top three commercial herbal antimalarial preparations in the Kumasi metropolis, Ghana

PURPOSE

Safety data on commonly used herbal medicinal (HM) products (HMPs) and marketed in Ghana are scarce. We assessed the sub-chronic toxicity of three most-patronised commercial antimalarial HMPs in Kumasi, Ghana.

METHOD

Top three HMPs (designated as herbal products 'A' (HPA), 'B' (HPB) and 'C' (HPC)) were selected after a mini-survey and sub-chronic toxicity evaluation conducted in accordance with Organisation for Economic Co-operation and Development (OECD) 407 guidelines. Control rats received clean water while test groups received daily adult human dose (DAHD), 5× DAHD or 10× DAHD of either HPA, HPB or HPC for 30 days. Rats were killed on day 31 to obtain biochemical, haematology and histology samples for analysis. Data were analysed by one-way analysis of variance (ANOVA) and post hoc Tukey's test.

RESULTS

The three HMPs produced alterations in liver morphology predominantly characterised by prominent foci of fatty change with scattered hepatocytes containing intracytoplasmic fat globules and congested central veins and sinusoids. The lungs showed alveolar with evidence of inflammation and foci of epithelial sloughing. Alveolar spaces were also obscured by debris and inflammatory cells. HPA and HPC produced scattered intensely congested heart vessels while HPB(10) produced haemorrhage and amorphous exudates within the heart. All HMPs produced neither treatment-related deaths nor significant change in haematological and biochemical parameters, except for HPA and HPB which decreased (P<0.05) aspartate aminotransferase (AST) and HPB, which elevated (P<0.05) fasting blood glucose (FBG).

CONCLUSION

Data from the present study suggest the potential of the herbal products (HPs), HPA, HPB and HPC, to cause major organ-system dysfunction or damage. We advise cautious use of these products and recommend further safety evaluation in chronic toxicity models.

Subacute oral toxicity of ayurvedic anti-diabetic preparation Jambadyarista in Sprague-Dawley rats

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Jambadyarista, an Ayurvedic formulation used in the management of diabetes and its related complications.

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This study investigated the subacute oral toxicity of Jambadyarista in a rat model.

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Biochemical and hematological parameters were studied after 28-day of treatment.

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Evidence of mortality and change in observed parameters were not seen that proves the oral safety of Jambadyarista.

Background

Jambadyarista is an Ayurvedic polyherbal formulation widely prescribed by Ayurvedic practitioners for the management of diabetes and its associated complications. About 39 companies have marketed this formulation in Bangladesh with consent from the Directorate General of Drug Administration (DGDA).

Aim

This study investigated the sub-acute oral toxicity of Jambadyarista in the Sprague-Dawley rat model.

Methods

The sub-acute toxicity studies were executed in Sprague-Dawley rats. Jambadyarista formulation was given for 28-days through oral gavage at 10 mL/kg and 20 mL/kg dose to two different groups comprising 6 rats of both sex/groups. Across the experimental period mortality, adverse reactions were closely monitored. After 28-day feeding hematological, biochemical, and relative organ weights were quantified.

Results

No mortality and/or signs of morbidity were observed for 28-day of repeated-dose sub-acute toxicity. Any pernicious change in body weight, biochemical, and hematological parameters along with relative organ weight were not observed for Jambadyarista. Correlation study among parameters of the renal profile, liver profile, lipid profile also metabolic hormones (T₃ and TSH), and enzymes showed the non-toxic rather beneficial role (hypolipidemic) of Jambadyarista in Sprague-Dawley rats.

Conclusion

Jambadyarista preparation did not cause any potential toxic effect in repeated dose subacute toxicity study over Sprague-Dawley rats orally. Therefore, low dose administration of Jambadyarista could have a beneficial effect on diabetes and can be considered safe before the chronic study.

Leaf and root bark extracts of Ziziphus abyssinica Hochst ex. A. Rich (Rhamnaceae) ameliorate hepatic, renal and splenic injuries induced by phenylhydrazine in rats

Objectives Ziziphus abyssinica (ZA) is employed in managing several ailments in Traditional African Medicine. Scientific evaluations are necessary to ascertain the medicinal potential of ZA as a source of new drug molecules. This study investigated the possible therapeutic benefit of ZA leaf (ZAL) and root bark (ZARB) extracts in an experimental model of multi-organ injuries induced by phenylhydrazine (PHZ). Methods Hyperbilirubinaemia, hepatotoxicity, nephrotoxicity and splenic injuries were induced by pretreating albino rats with PHZ (40 mg/kg, p.o.) for two alternate days. Afterward, six out of the eight groups of rats (n = 5) used were treated with either ZAL or ZARB (30, 100 and 300 mg/kg/day, p.o.) for seven days. Naïve control rats received saline without PHZ whereas negative control group received saline after PHZ. After one week of treatment, rats were sacrificed and blood collected for assessment of haematological and biochemical parameters. Liver, kidney and spleen sections were processed for histology and examined under light microscope. Results Data indicate that PHZ significantly (p < 0.05) increased total bilirubin, serum alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen (BUN), creatinine and BUN/creatinine ratio whereas red blood cell count was significantly reduced. These anomalies were significantly reversed in rats treated with ZAL or ZARB. The therapeutic effect of the extracts was supported by photomicrographs of the liver, kidney, and spleen of rats which revealed recovery from PHZ-mediated pyknosis, glomerular degeneration and multiple splenic necrosis respectively. Conclusions Overall, data from this study suggest that ZA may be useful in multiple organ injuries associated with PHZ-like xenobiotic toxicity.

Safety Assessment of Vanillic Acid: Subacute Oral Toxicity Studies in Wistar Rats

OBJECTIVES

Vanillic acid (VA) is a flavoring agent, a phenolic acid, and an intermediary by-product formed during transformation of ferulic acid to vanillin. It has been investigated for diverse pharmacological actions and used in Chinese medicine for decades. However, there is no information in the literature about its mechanism of toxicity or safety with long-term use. The present study will not only supply information on its pharmacological profile but also encourage evidence-based pharmacotherapeutic use. Hence, we performed a subacute toxicity study.

MATERIALS AND METHODS

According to the Organisation for Economic Co-operation and Development Test Guideline 407 (2008), 3 groups of rats were formed consisting of 12 rats (6 male and 6 female) in each group. For the subacute toxicity, the dose was chosen after a limit test was conducted. VA (1000 mg/kg/day) was orally administered for 2 weeks to the treatment group, whereas the control group received an equivalent volume of the vehicle. To assess reversibility, VA (1000 mg/kg/day, p.o.) was administered to the satellite group for 2 weeks and animals were observed for an additional 2 weeks after treatment. The adverse signs, variation in body weight, and mortality were evaluated throughout the study period. On days 15 and 29, blood was collected to evaluate essential biochemical and hematological parameters. The animals were subsequently weighed and sacrificed. The weights of internal organs were recorded; gross necroscopy and histopathological studies were performed.

RESULTS

The hematological parameters of the satellite group increased and the serum sodium level decreased after the treatment. Satellite groups showed no other major change in biochemical parameters when compared to the control group. In addition, relative organ weights, gross necropsy examinations and histopathological structure of the internal organs showed no major alterations.

CONCLUSION

VA showed no adverse effect on the process of leukopoiesis, erythropoiesis or on internal organs, as verified by hematological and biochemical evaluations, gross necropsy, and histopathological studies. The decrease in serum sodium is not considered as a major toxic effect.

Low-dose heavy metal mixture (lead, cadmium and mercury)-induced testicular injury and protective effect of zinc and Costus afer in wistar albino rats

The study evaluated the protective effect of Costus afer on low-dose heavy metal mixture (LDHMM)-mediated effects in the testis of albino rats. The weight-matched animals were divided into six groups: normal control, metal mixture of (PbCl₂  + CdCl₂ + HgCl₂ ), combination of metal mixture + Costus afer at 750 mg/kg, combination of metal mixture + Costus afer at 1,500 mg/kg, combination of metal mixture + Costus afer at 2,250 mg/kg and combination of metal mixture + (ZnCl₂ ). LDHMM reduced (p < .05) the antioxidant biomarkers (superoxide dismutase, SOD; catalase, CAT; and glutathione, GSH) and increased (p < .05) the lipid peroxidation marker (malondialdehyde, MDA) and lead, cadmium and mercury concentrations in the testis. Treatment with LDHMM increased (p < .05) abnormal sperm morphology and plasma prolactin (PRL) level and decreased epididymal sperm count, viability, follicle-stimulating hormone (FSH), luteinising hormone (LH) and testosterone. LDHMM exposure caused deleterious changes in the testis. Treatment of rats with Costus afer (750, 1,500 and 2,250 mg/kg) dose-dependently reduced (p < .05) the LDHMM-mediated toxicity. Treatment with Costus afer also reversed the testicular weight and LDHMM decrease in antioxidant biomarkers. Costus afer may be a defensive modulator of LDHMM-mediated testicular lesions.

In Vitro and In Vivo Toxicity Studies on Cymbopogon giganteus Chiov. Leaves Essential Oil from Benin

Cymbopogon giganteus Chiov. (Poaceae) is a medicinal plant used to treat various diseases in traditional medicine in several African countries. The present study aims to evaluate the oral and inhalation toxicity as well as the mutagenic effects of the essential oil of Cymbopogon giganteus leaves (EOCG) from a sample collected in Benin. Mutagenic potential was assessed by the Ames test using Salmonella typhimurium strains TA98 and TA100. Oral acute toxicity was carried out by administration of a single dose of 2000 mg/kg b.w. to Wistar rats while oral subacute toxicity was assessed by daily administration of 50 and 500 mg/kg of EOCG for 28 days. Finally, inhalation toxicity was assessed by administration of a single dose of 0.125%, 0.5%, 2% or 5% v/v of EOCG emulsions in 0.05% v/v lecithin solution in sterile water for the first experiment, and in a second one by administration of single dose of 0.125% or 0.5% v/v. A broncho-alveolar lavage was performed after 3 h or 24 h, respectively. The results show that EOCG is not mutagenic on Salmonella typhimurium strains at the highest concentration tested (200 μg/plate). In the acute oral toxicity study, EOCG induce neither mortality nor toxicity, showing that the LD₅₀ is greater than 2000 mg/kg. The subacute oral toxicity study at both doses did not show any significant difference in body weight, relative organ weight, hematological and/or biochemical parameters or histopathology as compared to the control group. EOCG induced mortality and inflammation in lungs 3 h after administration of a single dose of 5% or 2% v/v. Single doses of 0.125% or 0.5% v/v did not induce inflammation, cell recruitment nor cytotoxicity in lungs 3 h or 24 h after administration, suggesting safety at these concentrations. This first report on the in vivo toxicity will be useful to guide safe uses of EOCG.

Disruptions in the female reproductive system on consumption of calcium carbide ripened fruit in mouse models

This study investigated for the first time the outcome of ingestion of calcium carbide-ripened fruit on some female reproductive parameters. A set of unripe mature bananas ripened with calcium carbide (CCRB) and another set ripened via non-artificial means (NARB) were fed orally to prepubertal female mice for three days using the uterotrophic assay procedure. A distilled water group and oestradiol group (10 mg/kg) were also assigned. Food intake, body weights, vaginal openings and cytology were analysed. Samples of blood, uteri, ovaries and cervices were additionally collected and analysed. Increased serum oestrogen level and uterus weight were detected in the CCRB and oestradiol treated groups. Histopathology showed increased numbers of myometrial cells, presence of secondary follicles and regressing corpus lutea as well as thickened cervix epithelia which were evidence of oestrogenic disruptions. This study has shown that consumption of fruits ripened with calcium carbide negatively alters the female reproductive physiology, accelerates puberty onset and increases serum oestrogen levels. Caution must therefore be exercised by fruit sellers in the use of calcium carbide and policies set in place for strict regulation of its use worldwide.

Safety evaluation of syringic acid: subacute oral toxicity studies in Wistar rats

Syringic acid (SA) is a phenolic acid and have been investigated for diverse pharmacological activities, but the safety and/or mechanism of toxicity is still lacking in the literature. Subacute toxicity studies will add value to its pharmacological profile and support its exploration as a future medicine. According to OECD TG 407 (OECD, 2008), rats were divided into 3 groups (n = 12). The dose of SA was decided by limit test. Treatment and satellite groups received SA (1000 mg/kg/day, p.o for 14 days), whereas an equal volume of vehicle was given to control groups. In order to access reversibility, satellite groups were kept for another 14 days post-treatment. The toxic signs, mortality and body weight changes were recorded. On day 15 and 29 the rats were anesthetized to collect blood for estimation of hematological and biochemical parameters and then sacrificed to collect internal body organ for weighing and histopathological studies. SA has no major adverse effect on the body weight, food intake, erythropoiesis, leucopoiesis and on internal body organs which was confirmed by evaluating various biochemical and hematological parameters, relative body organ weight and histopathological studies. Therefore, SA could be considered safe over limited period of time and this study may help researchers in establishing the doses for the longer-term subchronic studies. Further, subchronic and chronic toxicity studies are required to evaluate safety on long term use.

Antimicrobial and toxicological evaluation of ethanol leaf extract of Salacia lehmbachii

The leaves of Salacia lehmbachii are used ethnomedically across Africa for the treatment of different diseases its antimicrobial activity as well as toxicological profile were evaluated. Antimicrobial activity against clinical strains of Pseudomonas aeruginosa, Salmonella typhi, Staphylococus aureus, Shigella species, Eschericha coli and Proteus mirabilis were compared with Gentamycin. Toxicological investigation was determined by administering 100 mg/kg, 200 mg/kg and 400 mg/kg of the ethanol leaf extract to male Wistar rats for 21 days with distilled water as control. Hematological and biochemical parameters as well as the vital organs were examined. The ethanol extract inhibited the growth of P. aeruginosa, S. typhi, S. aureus, Shigella species, E. coli and P. mirabilis to varying extents. The LD₅₀ in rats was greater than 5000 mg/kg. Toxicological evaluation of the extract did not produce any significant effect on hematological and biochemical parameters and vital organs in rats. S. lehmbachii ethanol leaf extract did not demonstrate antimicrobial activity against selected microorganisms. Neither did it show any non-toxic effect on the parameters investigated in rats. Thus the extract can be considered safe when administered orally.

Safety assessment of Oryeong-san, a traditional herbal formula: Study of subacute toxicity and influence of cytochrome P450s and UDP-glucuronosyltransferases

Oryeong-san is a traditional herbal formula that is used for the treatment of common genitourinary diseases in Korea and other Asian countries. However, little is known about its safety and influence on drug metabolism. In the present study, we investigated the subacute toxicity of an Oryeong-san water extract (OSWE) in rats and its effects on activities of drug-metabolizing enzymes. Subacute toxicity was modeled in animals exposed to treatment with the extract at multiple doses. Rats were given OSWE by oral gavage at 0, 1000, 2000 and 5000 mg/kg/day for 4 weeks. We checked general observations and investigated any changes of body/organ weight, food consumption, hematology, serum biochemistry, and urinalysis in vivo; and the activities of human microsomal cytochrome P450s (CYP450s) and UDP-glucuronosyltransferase (UGT) isozymes in vitro. We found that OSWE caused no significant toxicological changes at the doses tested. Therefore, the no observed adverse effect level of OSWE was more than 5000 mg/kg/day for male and female rats. OSWE inhibited the activities of CYP2C19 (IC₅₀: 737.69 μg/mL) and CYP2E1 (IC₅₀: 177.77 μg/mL). These results indicate that OSWE may be safe with no drug-related toxicity for up to 4 weeks and provide useful information concerning its potential to interact with conventional drugs or other herbal medicines.

Acute and sub-chronic toxicity evaluations of aqueous extract from stem bark of Grewia mollis (Malvaceae) in rats

Introduction: Different parts of Grewia mollis Juss. (Malvaceae) are commonly used in folk medicine to treat several ailments, including diarrhea, ulcers, rickets, cough and fever. Although several studies have proved its therapeutic effectiveness, there are very few toxicological studies on the plant. Objectives: This study was carried out to evaluate the acute and sub-chronic toxicity of the aqueous extract of G. mollis stem bark (GM) in animals. Methods: In the acute study, rats were orally administrated with GM at doses of 150, 300, 600, 1200, 2400, 4800 and 9600 mg/kg to determine the oral medial lethal dose (LD50). In the chronic study, rats received three doses of GM (150, 300 and 600 mg/kg) for 28 days. After the treatments, food intake, body weights, biochemical, hematological and histopathological parameters were analyzed. Results: The LD50 was estimated to be >9600 mg/kg. No significant alterations in the animal’s body weight gain, relative organs weight, serum biochemical analysis, hematological or histopathological analyses of liver, kidneys, lungs, heart and spleen were observed. Conclusions: The results of this study provided evidence that oral administration of GM at dose of 600 mg/kg is relatively safe in rats and may not exert severe toxic effects.

Evaluation of Acute and Subacute Oral Toxicity Induced by Ethanolic Extract of Marsdenia tenacissima Leaves in Experimental Rats

The objective of this study is to evaluate the acute and subacute toxicity of the ethanolic extract of Marsdenia tenacissima (MTE) leaves (family: Asclepiadaceae) in albino rats. The acute toxicity was performed where the limit dose of 5000 mg/kg body weight used. Observations were made and recorded for 24 h, and once daily further for a period of 14 days. The rats were weighed and various observations, like mortality, behavior, injury, or any signs of illness were conducted once daily during the period. For subacute study, four groups of 10 animals (female rats) received 10% Tween 20 in distilled water (control), and 250, 500, and 1000 mg/kg of freshly-prepared extracts, respectively, every 24 h orally for 28 days. At the end of each study, hematological analysis and biochemical parameters were evaluated. Histopathological examination of vital organs of the animals were taken for gross findings, compared to controls. There was no significant difference (p > 0.05) observed in the relative organs, body weights, hematological, biochemical parameters, and gross abnormalities, compared to the control. No mortality was recorded. Therefore, analysis of results may lead to the conclusion that the medium-term oral administration of the MTE leaves for 28 days does not cause toxicity.

Nonclinical Safety Assessment of Morus alba L. Fruits: Study of 90-D Toxicity in Sprague Dawley Rats and Genotoxicity in Salmonella

Morus alba L. is a traditional herb with a long history of consumption, both as an edible fruit and as medicine. However, its safety evaluation has not yet been established. The objective of this study was to evaluate subchronic oral toxicity and genotoxicity of M. alba L. fruits (MFE). The subchronic toxicity after daily oral administration of MFE at 0, 40, 200, and 1000 mg/kg for 90 d was examined in Sprague Dawley (SD) rats. MFE administration did not lead to death, adverse effects, change in food and water consumption, and body weight gain. Significant toxic effects were not found within the parameters of organ weight, biochemical values, and hematological and urine analysis between the control and the MFE group. The genotoxicity of MFE was assayed by Ames test in Salmonella typhimurium strains TA98, TA102, and TA1535. No genotoxicity was found in all the tested strains. Thus in this study, a no-observed-adverse-effect level for MFE in 90 d repeated oral toxicity study in rats was determined to be greater than 1000 mg/kg regardless of gender. The results also suggested that MFE does not have a genotoxicity potential.

Identification of structural alerts for liver and kidney toxicity using repeated dose toxicity data

BACKGROUND

The potential for a compound to cause hepatotoxicity and nephrotoxicity is a matter of extreme interest for human health risk assessment. To assess liver and kidney toxicity, repeated-dose toxicity (RDT) studies are conducted mainly on rodents. However, these tests are expensive, time-consuming and require large numbers of animals. For early toxicity screening, in silico models can be applied, reducing the costs, time and animals used. Among in silico approaches, structure-activity relationship (SAR) methods, based on the identification of chemical substructures (structural alerts, SAs) related to a particular activity (toxicity), are widely employed.

RESULTS

We identified and evaluated some SAs related to liver and kidney toxicity, using RDT data on rats taken from the hazard evaluation support system (HESS) database. We considered only SAs that gave the best percentages of true positives (TP).

CONCLUSIONS

It was not possible to assign an unambiguous mode of action for all the SAs, but a mechanistic explanation is provided for some of them. Such achievements may help in the early identification of liver and renal toxicity of substances.

Genotoxicity, acute and subchronic toxicity studies of nano liposomes of Orthosiphon stamineus ethanolic extract in Sprague Dawley rats

Background

Orthosiphon stamineus (OS) Benth is a medicinal plant and native in Southeast Asia. Pharmacological effects of OS are attributed to the presence of lipophilic flavones. However; lipophilic compounds suffer from poor aqueous solubility which limits the OS oral bioavailability and therapeutic applications. Therefore, OS was prepared in nano formulation form using liposomes from soybean phospholipids. The aim of the present study is to evaluate the in vitro genotoxicity and in vivo oral toxicity of nano liposomes of OS ethanolic extract (OS-EL).

Methods

In the acute toxicity study Sprague Dawley female rats were given a single dose of the OS-EL at 5000 mg/kg/day orally and screened for two weeks after administration. In the subchronic study, three different doses of OS-EL were administered for 28 days. Mortality, clinical signs, body weight changes, hematological and biochemical parameters, gross findings, organ weights, and histological parameters were monitored during the study. Genotoxicity was assessed using the Ames test with the TA98 and TA100 Salmonella typhimurium strains. High-performance liquid chromatography was performed for identification and quantification of the major marker compounds in OS-EL. Heavy metal detection was performed using an atomic absorption spectrometer.

Results

The acute toxicity study showed that the LD₅₀ of the extract was greater than 5000 mg/kg. In the repeated dose 28-day oral toxicity study, the administration of 250 mg/kg, 500 mg/kg, and 1000 mg/kg/day of OS-EL per body weight revealed no significant difference in food and water consumptions, bodyweight change, haematological and biochemical parameters, relative organ weights, gross findings or histopathology compared to the control group. The Ames test revealed that the OS-EL did not have any potential to induce gene mutations in S. Typhimurium.

Conclusions

Analyses of these results with the information of signs, behaviour, and health monitoring could lead to the conclusion that the long-term oral administration of OS-EL for 28 days does not cause sub-chronic toxicity.

Contribution to the food products' analysis: A research and evaluation on the hemolytic effect of some pesticides used in Lebanon

Pesticides are a real concern for the society as their use has become critical, leading sometimes to their accumulation as residues in fruits and vegetables. After examining the pesticides sold in Northern Lebanon, this study is focused on the analysis and identification of pesticides residues in fruits and vegetables that are harvested in this region and treated with the locally sold pesticides. Results show: first, (i) a use of Zineb by the name of another pesticide Micronized Sulfur to avoid prosecution; (ii) a significant presence of Metalaxyl in lemons and oranges; (iii) a significant presence of Trifluralin in strawberries; and (iv) a significant presence of Zineb in lemons and tomatoes. Second, with the use of hemolytic tests on human blood results show: (i) a critical concentration and a significant hemolytic effect of some pesticides used in Lebanon; and (ii) an absence of hemolytic effect in the collected fractions of the different analyzed fruit extracts containing pesticides. Finally, this work is the first step for pesticides' analysis in vegetables and fruits in Lebanon, initiating a wider analytical study in order to control and examine the use of pesticides which, according to our results, could have an adverse effect on human health over a long term.

Evaluating the enantioselective degradation and novel metabolites following a single oral dose of metalaxyl in mice

Metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-D,L-alaninemethylester] is a systemic fungicide widely used in agriculture. In this study, the enantioselective distribution, degradation and excretion of metalaxyl were investigated after oral gavage administration of rac-metalaxyl to mice. Concentration of metalaxyl and its enantiomers was determined by HPLC-MS/MS. The results showed that R-metalaxyl was much higher than S-metalaxyl in heart, liver, lung, urine and feces. As for the strong first pass effect, concentrations of metalaxyl in liver were much higher than those in other tissues. The total body clearance (CL) of metalaxyl in mice was 1.77 L h(-1 )kg(-1) and degradation half-lives of (t1/2) of S-metalaxyl and R-metalaxyl in liver were 2.2 h and 3.0 h, respectively. Such results indicated the enantioselectivity of metalaxyl lies in distribution, degradation and excretion processes in mice. Main metabolites were also determined and biotransformation reactions were hydroxylation, demethylation and didemethylation. Furthermore, metabolite concentrations in urine and feces were much higher than those in tissues. These results may have potential implications to predict toxicity and provide additional information associated with adverse health effects for risk assessment of metalaxyl.

Effect of aqueous leaves extract of Costus afer Ker Gawl (Zingiberaceae) on the liver and kidney of male albino Wistar rat

BACKGROUND

The use of medicinal plants in Nigeria has significantly increased over recent years as it is easily accessible, cheap and the strong belief that herbal remedies are natural and therefore non toxic.

AIMS

This study aims to investigate the sub-chronic toxicity (28-day) of the aqueous extract of Costus afer Ker Gawl leaves on the liver and kidney of male albino Wistar rats.

MATERIALS AND METHODS

A total of 20 male albino Wistar rats (113-205 g) divided into four groups of five weight-matched animals each, were used for the study. Group 1 received standard feed and water ad libitium and served as the control. Group 2, 3 and 4 received 375, 750 and 1125 mg/kg of aqueous extract of C. afer leaves respectively. The animals were sacrificed under ether anesthesia and the organs were harvested, weighed and histopathological studies carried out. The effect of C. afer on the hepatic biomarkers aspartate aminotransferase (AST), alanine aminotransferase (ALT); alkaline phosphatase (ALP); triglyceride (TG); total bilirubin (TB); conjugated bilirubin (CB); albumin (ALB) and kidney biomarkers urea, creatinine, sodium, potassium and bicarbonate were investigated.

STATISTICAL ANALYSIS

Data were evaluated using Mann Whitney. If P ≤ 0.05 groups were considered to be significantly different.

RESULTS

C. afer contained alkaloids, saponins, flavonoids, anthraquinones, cardiac glycosides, terpenoids, phenolic compounds and tannins. The average body, organ, relative weights, feed and fluid intake showed no significant changes (P > 0.05) when compared to the control. The liver function tests (ALT, ALP, AST, CB, TB and ALB) showed significant differences (P < 0.05) in the test groups when compared with the control while TG showed no statistical difference (P > 0.05). The kidney function tests (urea, creatinine, sodium, potassium and bicarbonate) showed no significant differences (P > 0.05) in the test groups when compared to the control.

CONCLUSION

Costus afer may be hepatotoxic but non-toxic to the kidney.

Acute and subchronic toxicity study of Euphorbia hirta L. methanol extract in rats

Despite Euphorbia hirta L. ethnomedicinal benefits, very few studies have described the potential toxicity. The aim of the present study was to evaluate the in vivo toxicity of methanolic extracts of E. hirta. The acute and subchronic oral toxicity of E. hirta was evaluated in Sprague Dawley rats. The extract at a single dose of 5000 mg/kg did not produce treatment related signs of toxicity or mortality in any of the animals tested during the 14-day observation period. Therefore, the LD 50 of this plant was estimated to be more than 5000 mg/kg. In the repeated dose 90-day oral toxicity study, the administration of 50 mg/kg, 250 mg/kg, and 1000 mg/kg/day of E. hirta extract per body weight revealed no significant difference (P > 0.05) in food and water consumptions, body weight change, haematological and biochemical parameters, relative organ weights, and gross findings compared to the control group. Macropathology and histopathology examinations of all organs including the liver did not reveal morphological alteration. Analyses of these results with the information of signs, behaviour, and health monitoring could lead to the conclusion that the long-term oral administration of E. hirta extract for 90 days does not cause sub-chronic toxicity.

Effects of nimesulide on testicular functions in prepubertal albino rats

BACKGROUND

Daily consumption of painkillers has almost become a routine in many parts of Africa and Asia due to manual labor, especially in young adults. In view of the wide-scale use of painkillers in many parts of Africa and Asia, it is feared that the use of nimesulide may constitute an appreciable public health risk. The present work is aimed at assessing the long-term testicular toxicity of nimesulide in growing male albino rats.

METHODS

Male albino rats aged 4-5 weeks and weighing between 36 and 42 g were obtained from the Toxicology Unit of the Department of Pharmacology, Faculty of Pharmacy University of Nigeria, Nsukka, Nigeria. The animals were housed singly in a cross-ventilated room at a temperature 22°C±3°C and a 12-h light/12-h dark cycle. They were fed with standard rat pellets (Pfizer Pharmaceuticals, Ikeja, Nigeria) and were given water ad libitum. The rats were divided into three groups of five rats each: the first and second groups orally received 5 and 7.5 mg/kg/day of nimesulide, respectively, whereas the third group did not receive any drug and acted as controls for 56 days. Weekly body weight of each rat was taken. Blood samples were collected on the 56th day by cardiac puncture, and serum samples were frozen until analysis. Rats were sacrificed under ether anesthesia. Epididymal semen number was counted using a Neubauer counting chamber. Sperm motility was assayed microscopically within 5 min at 37°C. Estradiol and testosterone were analyzed with electrochemiluminescence immunoassay using Elecsys autoanalyzer, model 1010 (Roche, Mannheim, Germany). The testes were excised, weighed, and fixed in Bouin fluid and processed for histopathology.

RESULTS

Treatment with nimesulide did not significantly affect body weight, absolute and relative testis weights, or epididymal sperm number, but there were significant differences in testosterone and estradiol levels. At the doses studied, there were no significant changes in testicular architecture except for mild degenerative changes.

CONCLUSIONS

In conclusion, nimesulide at normal therapeutic doses may not be spermatoxic, but it is feared that at higher doses, it may have testicular toxicity in albino rats.

Toxicity of dietary melamine to laying ducks: biochemical and histopathological changes and residue in eggs

Jinding laying ducks (n = 648) were subjected to one of six dietary treatments (0, 1, 5, 25, 50, or 100 mg of melamine/kg of diet) to investigate the toxicity of melamine and determine the melamine residue in eggs. Ducks were fed melamine-supplemented diets for 21 days followed by a 21 day withdrawal period. Dietary melamine had no adverse effects on laying performance. Renal lesions were correlated with increasing levels of dietary melamine. Melamine residue in eggs increased with dietary melamine during the first 21 days and reached the maximum content (1.35 mg/kg) in the 100 mg of melamine/kg of diet group. Melamine residue in eggs decreased rapidly during the withdrawal period. The depletion time for egg melamine residue increased with dietary melamine level. These results indicated that a dietary level of > or = 50 mg of melamine/kg of feed induces obvious renal injury. The residue level and withdrawal time for melamine clearance in eggs correlated with the dietary melamine level.

Hepatotoxic and hematologic effects of an aqueous extract of the Nigerian herbal remedy U&D Sweet Bitter in male albino rats

The hepatotoxic and hematologic effects of the extract of a Nigerian herbal remedy, U&D Sweet Bitter, were investigated in mature Wistar albino rats. Twenty male albino rats were allocated into four dose groups of five rats each. Food and fluid intake, body weight, absolute and relative weight of the liver, and hematologic and biochemical parameters were measured. The absolute and relative weights of the liver significantly decreased (p < or = .05) when compared with controls. Doses of 539, 1077, or 1616 mg/kg of U&D Sweet Bitter given orally for 90 d induced a significant (p < .05) dose-dependent increase in aspartate aminotransferase and alkaline phosphatase and decrease in alanine aminotransferase compared with controls. Hepatic and haematologic parameters of treated groups were significantly different from those of controls. Histologic examination revealed that U&D Sweet Bitter induced severe necrosis and edema.

Nephrotoxic effects of aquoeus extract U & Dee Sweet Bitter (a Nigerian herbal remedy) in male albino rats

The effect of the extract of U & Dee Sweet Bitter, a Nigerian herbal remedy on the kidney was investigated in matured Wistar albino rats. Twenty male albino rats were allocated into four dose groups of five rats each, namely 0.00, 539, 1077, 1616 mg/kg of the herbal product orally for 90 days. Animals had access to deionized water and were fed ad libitum with rat chow for 90 days. The feed and fluid consumption of the animals were measured on daily basis, and the body weight was measured weekly. After 90 days, the animals were anaesthetized with ether, bled, sacrificed, kidney excised, and weighed. The parameters measured included food and fluid intake, body weight, absolute and relative weight of the kidney. A nonsignificant increase (p > .05) in feed and fluid intake occurred in all treated animals and a significant decrease (p < .05) in absolute weight of the kidney in all the treated animals when compared with the control. The administration of 539, 1077, and 1616mg/kg of U & Dee Sweet Bitter caused a significant (p < .05) dose-dependent increase in creatinine, whereas a significant dose-dependent decrease for urea was noted compared with the control. Histological study showed that U & Dee Sweet Bitter at all doses caused renal pathologic changes that include tubular necrosis, inflammation of the interstitial and glomerulus, and disorganization of the entire architecture. The results are indicative of nephrotoxicity.

Effects of subchronic exposure via drinking water to a mixture of eight water-contaminating metals: a biochemical and histopathological study in male rats

In the current study, we examined whether subchronic exposure via drinking water to low doses of a mixture of metals (arsenic, cadmium, lead, mercury, chromium, manganese, iron, and nickel), found as contaminants in various water sources of India, and to concentrations equivalent to WHO maximum permissible limits (MPL) in drinking water for individual metals, can alter systemic physiology of male rats. Data on water contamination with metals in India were collected from the literature and metals were selected on the basis of their frequency of occurrence and contamination level above MPL. Male Wistar rats were exposed to the mixture at 0, 1, 10, and 100 times the mode concentrations (the most frequently occurring concentration) of the individual metals via drinking water for 90 days. One more group of rats was exposed to the mixture at a concentration equivalent to the MPL (WHO) in drinking water for individual metals. Toxic potential of the mixture was evaluated by assessing general toxicological end points, serum chemistry and histopathology of vital organs. The mixture decreased body weight and water consumption and increased weights of brain, liver, and kidneys with 10x and 100x doses. After 30 days of exposure, no appreciable changes were found in any blood clinical markers. After 60 days, only the 100x dose, while after 90 days both 10x and 100x doses increased activities of aspartate aminotransferase and alkaline phosphatase and levels of urea nitrogen and creatinine and decreased total protein and albumin levels, but alanine aminotransferase activity and glucose level were not affected. At 10x and 100x exposure levels, qualitatively similar, but dose-dependent vascular, degenerative, and necrotic changes were observed in brain, liver, and kidney. The results indicate that subchronic exposure to the metal mixture affected general health of male rats by altering the functional and structural integrity of kidney, liver, and brain at 10 and 100 times the mode concentrations of the individual metals in Indian water sources, but exposure at mode concentrations of contemporary water contamination levels or at concentrations equivalent to the MPL for individual metals in drinking water may not cause any health hazards in male rats.

Health of herring gulls (Larus argentatus) in relation to breeding location in the early 1990s. II. Cellular and histopathological measures

Organosomatic indices, hematological indicators of stress, and histopathological lesions were quantified for over 150 incubating herring gulls (Larus argentatus) sampled in 11 colonies throughout the Great Lakes and reference colonies in Lake Winnipeg and the Bay of Fundy. Of 21 parameters assessed, significantly more differed between Great Lakes colonies and reference colonies than between the two reference colonies. Relative adrenal, kidney, and liver masses of gulls from some Great Lakes colonies were reduced and thyroid masses increased relative to gulls from reference colonies. Foci of cellular atypia were observed in the hepatocytes of two Great Lakes gulls. Chronic periportal hepatitis, lipogranulomas and vacuolation of hepatocytes, and chronic granulomatous interstitial nephritis were more prevalent or severe in gulls from Great Lakes colonies and were associated with contaminants. The kidneys of gulls from the three most contaminated locations were damaged and functionally compromised. Interstitial nephritis was likely the most functionally significant histopathological lesion. Portal-tract fibrosis, granulomatous hepatitis, and kidney tubule dilation/obstruction and splenic enlargement were more prevalent or severe at reference sites and were associated with blood-borne parasites. Amyloid deposits were observed in the spleen, kidneys, or liver of nearly half of the gulls. Associations between the prevalence or severity of lesions and contaminant levels in gull tissues or the trophic level of their diet suggest some lesions are toxicopathic. Associations were most frequently found with planar halogenated aromatic hydrocarbons and lead. The stress response, as measured by the heterophil/lymphocyte ratio, was attenuated in gulls from Areas of Concern and associated with decreased adrenal mass. Our findings suggest that adult Great Lakes gulls suffered from chronic exposure to chemical stressors in the early 1990s sufficient to modulate endocrine function and physiological processes and induce structural changes in tissues.

Investigation into the Nephrotoxicity of Nigerian Bonny Light Crude Oil in Albino Rats

The effect of bonny-light crude oil was assessed in adult albino rats. The rats were administered with 200, 400, and 800 mg/kg body weight of the crude oil orally for 7 days. Fluid intake was measured daily, initial and final animal body was recorded. The toxic effects on the kidneys were assessed and histological studies carried out. The results revealed that the kidney cells were damaged; crude oil caused a destruction of the renal reserve capacity. There was a significant increase (p ? 0.05) in creatinine in the high dose group (800mg/kg), and a significant decrease (p ? 0.05) in urea concentration. Histological examination indicates that crude oil induced severe pathologic changes in the forms of necrosis and oedema.

Effects of rinbacin extract on rat kidney

The aqueous leaf extract of rinbacin was tested for toxic effects on prepubertal rat kidneys following chronic administration. Two doses of rinbacin extract (26.25 g/l and 52.50 g/l) were administered in the rats' drinking water for 13 weeks, and various toxicologic indices tested. Histological study of the kidneys was also carried out at the expiration of the test period. Rinbacin at both dose sizes significantly (p<0.05) increased the absolute and relative kidney weights. Also the serum HCO3- level was significantly (p<0.05) increased, while the serum K+ level was decreased significantly at both dose levels. Only the high dose significantly (p<0.05) increased the serum urea level of the rats. Histological study showed that rinbacin at both dose sizes caused renal pathologic changes, which included necrosis and cellular infiltration of glomeruli and epithelia of the tubules. The effects were less marked in the low dose than the high dose group. Chronic administration of rinbacin extract induces nephrotoxicity in young rats.

Nephrotoxic actions of low-dose mercury in mice: protection by zinc

The authors conducted this study to determine if very-low-dose (i.e., 4 ppm) mercury is nephrotoxic and, if so, whether the nephrotoxic actions of mercury in mice could be prevented by zinc intake. Animals were administered 4 ppm mercuric chloride and/or 800 ppm zinc chloride in their drinking water for 12 wk. The animals were sacrificed at the end of the exposure period, and their kidneys were excised, weighed, and processed for histological study. Both metals reduced significantly (p < .05) the absolute and relative kidney weights of the animals. Zinc-treated animals showed normal kidney histology that was comparable with that of the control. Mercury treatment produced necrosis and widening of the glomeruli, whereas a combination of both metals resulted in protection from the toxic effects, with most nephrons resembling the control. The results indicate that low-dose mercury exposure in mice kidney induces some degenerative effects, which are prevented by zinc.

Low-dose mercury induces testicular damage protected by zinc in mice

OBJECTIVES

This investigation was set out to determine whether mercury at a very low dose (4ppm) induces testicular damage on murine testis, and if so whether the toxic effects of mercury could be prevented by zinc.

STUDY DESIGN

One of the following solutions was administered in the drinking water of CD-1 male mice: (1) 4ppm HgCl(2); (2) 800ppm ZnCl(2); (3) 4ppm HgCl(2)+800ppm ZnCl(2); or (4) deionised water; for 12 weeks. At the expiration of the treatment period, animals were sacrificed, testes excised and weighed, and epididymal sperm number taken. The testes were processed for histological examination.

RESULTS

Both zinc and mercury significantly (p<0.05) decreased the absolute and relative testicular weights, with mercury producing the highest reduction in weight. Mercury reduced significantly (p<0.05) the epididymal sperm number, while zinc and mercury/zinc produced statistically same effect with control on the sperm number. Histological study showed that mercury at the concentration employed produced remarkable degenerative lesions on the testes, as the zinc-treated group showed a normal morphology. Majority of the animals in the mercury/zinc-treated group exhibited complete or partial protection as evidenced by the morphology of the seminiferous tubules.

CONCLUSION

Zinc prevents mercury-induced testicular damage in mouse. These findings highlight the risks exposure to inorganic mercury might pose to male reproduction of mice, and suggests possible therapy with zinc. Study in humans is therefore advocated.

Nephrotoxicity in rats undergoing a one-hour exposure to compound A

We previously demonstrated that rats experienced renal injury when exposed for 3-12 h to 50 ppm or more of a vinyl ether called Compound A [CF2 = C(CF3)OCH2F], a compound produced by CO2 absorbents acting on sevoflurane. These durations of exposure exceed the average duration of clinical anesthesia. We now report the effect of a 1-h exposure to 0, 100, 150, 200, 400, 600, or 800 ppm of Compound A in oxygen in 145 Wistar rats. Twenty-four hours after exposure, we obtained kidney and liver specimens for microscopic examination, applying hematoxylin and eosin, and (separately) an immunochemical marker (PCNA) for cell proliferation (regeneration). Compared with results from control rats (those breathing oxygen for 1 h), renal injury (defined as necrosis of the outer strip of the outer medullary layer or "corticomedullary junction necrosis") occurred at and above 200 ppm. Exposure to 150 ppm produced cell regeneration (i.e., stimulated cell proliferation). We conclude that the threshold concentrations for nephrotoxicity (i.e., minimal toxicity) for a 1-h exposure to Compound A exceed the maximum concentrations (particularly those at low inflow rates) reported in clinical practice by a factor of 2-3. If these threshold effects in rats apply to humans, one 1-h exposure to sevoflurane probably would not alter usual measures of renal function.

A multidisciplinary approach to toxicological screening: I. Systemic toxicity

The toxicity of 10 chemicals, including pesticides (carbaryl, chlordane, heptachlor, and triadimefon), solvents (carbon tetrachloride, dichloromethane, tetrachloroethylene, and trichloroethylene), and industrial chemicals [diethylhexylphthalate (DEHP) and phenol] was examined in the liver, kidneys, spleen, thymus, and adrenals of female F344 rats after 1 or 14 d of oral dosing. For each chemical, 4 doses were based on fractions of the acute LD50, which was estimated using an abbreviated (up-and-down) method. A multivariate analysis (MANOVA) was conducted for each organ using selected measures of toxicity. A post hoc contrast analysis was also conducted for significant MANOVA results in order to determine effective and ineffective doses. A single dose of heptachlor resulted in necrotic lymphocytes in the spleen and thymus at doses > or = 23 mg/kg. Triadimefon altered liver and spleen weights; this effect has not been described previously. Dichloromethane (> or = 337 mg/kg/d for 14 d) increased the incidence of necrosis of individual centrilobular hepatocytes. Trichloroethylene-induced hepatotoxicity was obtained at doses an order of magnitude lower than those reported in the literature. Acute DEHP (150 mg/kg) increased mitotic figures in hepatocytes, which were replaced by hepatocellular cytomegaly after 14 d of dosing at the same level. Following phenol exposure, there was an increased incidence in hepatocellular necrosis at 1 d, and an increased incidence of kidney lesions at 1 and 14 d; these findings were considered to be the result of vascular stasis. Overall, the algorithm used to select doses was effective for both 1- or 14-d dosing regimens. For all chemicals except carbon tetrachloride, the lowest effective dose for systemic toxicity was within the range of 3-56% of the LD50 for acute dosing, and 1-30% of the LD50 for repeated administration.

Clinical pathology testing recommendations for nonclinical toxicity and safety studies. AACC-DACC/ASVCP Joint Task Force

Clinical pathology testing in nonclinical toxicity and safety studies is an important part of safety assessment. In recent years, clinical laboratory testing has rapidly expanded and improved. Some government regulatory agencies provide guidelines for clinical pathology testing in nonclinical toxicity and safety studies. To improve these testing guidelines and the resultant safety assessments, the American Association for Clinical Chemistry's Division of Animal Clinical Chemistry and the American Society for Veterinary Clinical Pathology formed a joint committee to provide expert recommendations for clinical pathology testing of laboratory species involved in subchronic and chronic nonclinical toxicity and safety studies. These recommendations include technical recommendations on blood collection techniques and hematology, serum chemistry, and urinalysis tests.

Nephrotoxic effects of diethylene glycol (DEG) in rats

Diethylene glycol (DEG) is a widely used substance with various risks of intoxication. In adult rats influences of DEG on functional parameters are characterized, indicating early signs of nephrotoxicity. A dose dependent proteinuria, an oliguric effect, an increased excretion of free hydrogen ions and a compensated impairment of renal tubular transport processes can be stated (0.25, 0.5 and 0.75 ml DEG/100 g b.m. i.p.). Following a single dose of 0.5 ml DEG/100 g b.m. i.p. the maximally expressed nephrotoxic effect is measurable 4 to 8 days after administration.

Plasma clearance of 51Cr-EDTA as an estimator of glomerular filtration rate in conscious rats

A method is described whereby the plasma clearance of 51Cr-EDTA is used to estimate the glomerular filtration rate (GFR) in conscious rats. EDTA clearance rates were calculated based on one and two exponential disappearance curves and compared in groups of animals studied under conditions of normal, high and low GFR. Like previously described related methodologies, this technique obviates the need for urine collections and marker infusions for GFR estimates. An important added advantage is that it provides the opportunity to study animals free of the effects of anesthetic, supine position and surgical stress.

Assessment of renal function and damage in animal species. A review of the current approach of the academic, governmental and industrial institutions represented by the Animal Clinical Chemistry Association

There are a wide variety of laboratory tests available to assess damage to and functional impairment of the kidneys, although the effectiveness of these tests varies greatly depending upon the site specificity of the damage and to a lesser extent upon the animal species involved. Several traditional tests of renal dysfunction and damage, including plasma creatinine and urea, and urinalysis (dipstick and/or quantitative protein), can be used in the first instance to detect nephrotoxicity. A second tier of specific, targetted indicators (concentration test, urinary enzymes, clearance of analytes, specific proteins, etc.) may then be applied to identify further the site of the lesion and the functional status of the kidneys. The glomerular filtration rate (GFR) may be estimated from the clearance of exogenous and endogenous substances. The difficulty in obtaining accurately timed urine samples limits the value of these tests in small animals, although methods that do not involve urine collection are available. The kidney is the origin of several enzymes found in urine that can be used to monitor the toxic effects of chemicals and therapeutic substances. Selective measurement of enzyme activities in urine can be used to detect the site of the renal lesion after traditional tests have established the presence of renal injury. Separation of proteins in urine by electrophoretic techniques may also be used to discriminate damage to different parts of the nephron. Renal cell excretion in urine is a sensitive but unreliable indicator of acute damage to the proximal tubule. The rate of cell excretion is not a good predictor of the severity of tubular injury.(ABSTRACT TRUNCATED AT 250 WORDS)