Effect of metformin on germ cell-specific apoptosis, oxidative stress and epididymal sperm quality after testicular torsion/detorsion in rats.

The study was designed to evaluate the effects of metformin on apoptosis and epididymal sperm quality in a rat testicular ischaemia/reperfusion (I/R) injury model. A total of 72 male rats were divided into four groups (n = 18 for each group): group 1 (sham-operated group), group 2 (metformin group), group 3 (torsion/detorsion [T/D] + saline) and group 4 (T/D + 300 mg kg-1 metformin). Testicular torsion was achieved by rotating the right testis 720° in a clockwise direction for 1 hr. Tissue malondialdehyde (MDA) level and caspase-3 activity increased and the activities of catalase, superoxide dismutase and glutathione peroxidase decreased in comparison with sham-operated group 4 hr after detorsion (p < .001). In six rats of each group 24 hr after detorsion, histopathological changes and germ cell apoptosis were significantly deteriorated by measuring mean of seminiferous tubule diameters (MSTD) and TUNEL test. Moreover, 30 days after T/D, sperm concentration and motility were examined in six animals per group. Metformin pre-treatment reduced MDA and caspase-3 levels and normalised antioxidant enzyme activities 4 hr after detorsion, and germ cell apoptosis was significantly decreased, and the MSTD, as well as sperm functions, was significantly improved. Reduction in oxidative stress and apoptosis may have a major role in cytoprotective effects of metformin.

Nortriptyline protects testes against germ cell apoptosis and oxidative stress induced by testicular ischaemia/reperfusion.

We designed this experiment to evaluate the effects of nortriptyline on testicular injury after torsion/detorsion (T/D). Ninety-six adult Wistar rats were divided into six groups 16 each in control group (Group 1), sham operated (Group 2), T/D + saline (Group 3), and in groups 4-6; were administered 2, 10 and 20 mg kg-1 , i.p. of nortriptyline 30 and 90 min after torsion respectively. Testicular torsion was created by twisting the right testis 720° in clockwise direction for 1 h. In six rats of each group, tissue MDA level and caspase-3 activity increased and the activities of catalase, superoxide dismutase and glutathione peroxidase decreased in compared with control group 4 h after detorsion (P < 0.001). In six rats of each group 24 h after detorsion, histopathological changes and germ cell apoptosis were significantly deteriorated by measuring mean of seminiferous tubules diameters (MSTD) and TUNEL test. Moreover, 30 days after T/D, sperm concentration and motility were examined in rest of rats. Pre- and post-reperfusion nortriptyline could reduce MDA and caspase-3 levels and normalise antioxidant enzymes activities, dose dependently. Germ cell apoptosis was significantly decreased, and the MSTD, as well as sperm functions, were significantly improved. Inhibition of mitochondrial permeability transition pore is probably involved in protective effects of nortriptyline against testicular T/D cell damages.

Deferoxamine preconditioning to restore impaired HIF-1α-mediated angiogenic mechanisms in adipose-derived stem cells from STZ-induced type 1 diabetic rats.

OBJECTIVES: Both excessive and insufficient angiogenesis are associated with progression of diabetic complications, of which poor angiogenesis is an important feature. Currently, adipose-derived stem cells (ADSCs) are considered to be a promising source to aid therapeutic neovascularization. However, functionality of these cells is impaired by diabetes which can result from a defect in hypoxia-inducible factor-1 (HIF-1), a key mediator involved in neovascularization. In the current study, we sought to explore effectiveness of pharmacological priming with deferoxamine (DFO) as a hypoxia mimetic agent, to restore the compromised angiogenic pathway, with the aid of ADSCs derived from streptozotocin (STZ)-induced type 1 diabetic rats ('diabetic ADSCs'). MATERIALS AND METHODS: Diabetic ADSCs were treated with DFO and compared to normal and non-treated diabetic ADSCs for expression of HIF-1α, VEGF, FGF-2 and SDF-1, at mRNA and protein levels, using qRT-PCR, western blotting and ELISA assay. Activity of matrix metalloproteinases -2 and -9 were measured using a gelatin zymography assay. Angiogenic potential of conditioned media derived from normal, DFO-treated and non-treated diabetic ADSCs were determined by in vitro (in HUVECs) and in vivo experiments including scratch assay, three-dimensional tube formation testing and surgical wound healing models. RESULTS: DFO remarkably enhanced expression of noted genes by mRNA and protein levels and restored activity of matrix metalloproteinases -2 and -9. Compromised angiogenic potential of conditioned medium derived from diabetic ADSCs was restored by DFO both in vitro and in vivo experiments. CONCLUSION: DFO preconditioning restored neovascularization potential of ADSCs derived from diabetic rats by affecting the HIF-1α pathway.

Acute inhalation exposure to titanium ethanolate as a possible cause of metal fume fever.

Occupational inhalation exposure to noxious agents is not uncommon. Herein, we present a 26-year-old male student who had accidental acute inhalation exposure to a large quantity of titanium ethanolate and hydrogen chloride in chemistry lab. He was referred to the emergency department of our hospital with low-grade fever, dyspnea, headache, fatigue and myalgia. After 24 hrs of symptomatic treatment (oxygen therapy and acetaminophen), the fever was subsided and the patient discharged home in a good clinical condition. The presented symptoms could be interpreted as a form of metal fume fever. It can therefore be concluded that organo-metallic compound of titanium metal may have the potential to produce metal fume fever in human.

Intestinal obstruction in acute inhalational toluene 2,4-diisocyanate gas toxicity.

The isocyanates are widely used as precursors of polyurethane products, as well as carbamate insecticides. Toluene 2,4-diisocyanate (TDI) is one of the most important commercially used isocyanates. Humans may be exposed to TDI by inhalation, ingestion, dermal and eye contact. TDI is a powerful irritant to the mucosal membranes of the gastrointestinal and respiratory tracts, eyes and the skin. Pulmonary manifestations, especially occupational asthma, are the predominant manifestations after TDI toxicity. Herein, we present intestinal obstruction as an extraordinary manifestation of acute TDI toxicity after occupational exposure. TDI toxicity may cause intestinal obstruction.

Tropisetron diminishes demyelination and disease severity in an animal model of multiple sclerosis.

Tropisetron, a selective 5-HT3 receptor (5-HT3R) antagonist, has been widely used to counteract chemotherapy-induced emesis. New investigations described the immunomodulatory properties of tropisetron which may not be 5HT3R mediated. In the present study, we assessed the potential effects of tropisetron on an animal model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). EAE was induced in C57BL/6 mice by myelin oligodendrocyte glycoprotein peptide (MOG35-55) immunization. Animals were treated with tropisetron (5 mg/kg/day); m-chlorophenylbiguanide (mCPBG), a selective 5-HT3R agonist (10 mg/kg/day); tropisetron (5 mg/kg/day) plus mCPBG (10 mg/kg/day), and granisetron (5 mg/kg/day) intraperitoneally on days 3-35 post-immunization. Treatment with tropisetron and granisetron markedly suppressed the clinical symptoms of EAE (p<0.001) and reduced leukocyte infiltration as well as demyelination in the spinal cord (p<0.05). In addition, in vivo tropisetron, granisetron or tropisetron plus mCPBG therapy greatly reduced in vitro MOG35-55-stimulated proliferation of mononuclear cells from spleens, and MOG35-55-induced IL-2, IL-6 and IL-17 production by splenocytes isolated from EAE-induced mice (p<0.05). Concurrent administration of tropisetron and mCPBG did not significantly alter the histological damage in the spinal cord. mCPBG had no effect on the mentioned parameters. Taken together, these findings indicate that tropisetron has considerable immunoregulatory functions in EAE and may be promising for the treatment of MS or other autoimmune and inflammatory diseases of the CNS. Furthermore, beneficial effects of tropisetron in this setting seem to be both receptor dependent and receptor independent in the early phase of the disease.

Thalidomide attenuates multiple low-dose streptozotocin-induced diabetes in mice by inhibition of proinflammatory cytokines.

Thalidomide is an immunomodulatory and anti-inflammatory agent and is used in autoimmune disorders. It has been shown that thalidomide inhibits proinflammatory cytokines production. The purpose of this study was to investigate the effect of thalidomide on the prevention of autoimmune diabetes in mice. Diabetes was induced by multiple low-dose of streptozotocin (MLDS) injection. Mice were treated with thalidomide (300 mg/kg/day orally) for 21 days. Plasma levels of glucose, insulin and nitrate/nitrite as well as pancreatic cytokine levels were measured. Pathological examinations of the pancreas revealed that thalidomide reduced the islet inflammation (insulitis) and destruction of beta cells. Thalidomide treatment prevented hyperglycemia and preserved pancreatic insulin secretion in the diabetic mice. Thalidomide treatment also significantly decreased plasma levels of nitric oxide and pancreatic proinflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-6, IL-12, IL-17 and interferon (IFN)-γ)] while increased anti-inflammatory cytokine IL-10. In conclusion, these findings indicate that thalidomide may have a protective effect against the autoimmune destruction of the pancreatic beta-cells during the development of MLDS-induced type 1 diabetes in mice.

Monitoring dithiocarbamate fungicide residues in greenhouse and non-greenhouse tomatoes in Iran by HPLC-UV.

The simultaneous analysis of dithiocarbamate fungicide residues on greenhouse and non-greenhouse tomatoes was performed by high-performance liquid chromatography with UV detection. A calibration curve with spiked samples was plotted to determine dithiocarbamate residues in tomato samples. Limits of detection and quantification were approximately 0.05 and 0.2 µg g(-1), respectively. The ranges of mean recoveries at five spiking levels for all dithiocarbamates of interest were between 88.2%-95.7% and 99.5%-100.8% in standards and spiked samples, respectively. In this study, 40 greenhouse and 40 non-greenhouse tomato samples were analysed. None of the samples analysed contained dithiocarbamates in excess of the maximum residue levels established by the Codex Committee on Pesticide Residues, except for one greenhouse sample, with ethylenebisdithiocarbamates at 3.2 µg g(-1).

Methadone ameliorates multiple-low-dose streptozotocin-induced type 1 diabetes in mice.

Type 1 diabetes is an autoimmune disease characterized by inflammation of pancreatic islets and destruction of beta cells by the immune system. Opioids have been shown to modulate a number of immune functions, including T helper 1 (Th1) and T helper 2 (Th2) cytokines. The immunosuppressive effect of long-term administration of opioids has been demonstrated both in animal models and humans. The aim of this study was to determine the effect of methadone, a mu-opioid receptor agonist, on type 1 diabetes. Administration of multiple low doses of streptozotocin (STZ) (MLDS) (40 mg/kg intraperitoneally for 5 consecutive days) to mice resulted in autoimmune diabetes. Mice were treated with methadone (10 mg/kg/day subcutaneously) for 24 days. Blood glucose, insulin and pancreatic cytokine levels were measured. Chronic methadone treatment significantly reduced hyperglycemia and incidence of diabetes, and restored pancreatic insulin secretion in the MLDS model. The protective effect of methadone can be overcome by pretreatment with naltrexone, an opioid receptor antagonist. Also, methadone treatment decreased the proinflammatory Th1 cytokines [interleukin (IL)-1beta, tumor necrosis factor-alpha and interferon-gamma] and increased anti-inflammatory Th2 cytokines (IL-4 and IL-10). Histopathological observations indicated that STZ-mediated destruction of beta cells was attenuated by methadone treatment. It seems that methadone as an opioid agonist may have a protective effect against destruction of beta cells and insulitis in the MLDS model of type 1 diabetes.

Enzymuria determination in children treated with aminoglycosides drugs.

Although aminoglycosides antibiotics are used in children and adult commonly, they have serious side effects such as nephrotoxicity and ototoxicity. In clinical practice, for renal function, the levels of serum creatinine and blood urea nitrogen routinely are measured. Since these parameters have limitations such as unreliability, insensitivity, and nonspecificity, the rapid assessment of renal function based on these patients is very important. Increase in N-acetyl-beta-D-glucosaminidase (NAG), a hydrolytic lysosomal enzyme, suggests proximal tubular cell damage. In this study, 32 children aged 2 months through 2 years, treated with gentamicin and amikacin for suspected infections at the pediatric ward of Alborz hospital from September 2006 to February 2007, were enrolled. Serum and fresh urine before and after drug infusion were obtained on the 1st, 3rd, and 5th days of antibiotic treatment. Serum urea and creatinine with urinary creatinine, albumin, NAG, lactate dehydrogenase (LDH) and alkaline phosphatase (AP) activity were then determined. A statistically significant increase in urinary NAG, LDH, and AP on 5th day was found compared with before gentamicin administration (P < 0.001, P < 0.01, P < 0.05, respectively). The urinary NAG activity may be a useful indicator of renal injury in children treated with aminoglycosides drugs compared with other routine clinical indicators.

Alternative electron acceptors: Proposed mechanism of paraquat mitochondrial toxicity.

Paraquat (PQ) is a relatively safe and effective herbicide used all over the world. PQ is very toxic to all living organisms; and many cases of acute poisoning and death have been reported over the past decade. The main suggested potential mechanism for PQ toxicity is the production of superoxide radicals from the metabolism of the PQ by microsomal enzyme systems, and by inducing mitochondrial toxicity. Mitochondria are considered to be a major source of reactive oxygen species in cells and according to this hypothesis, PQ, through suitable oxidation and reduction processes, is able to participate in the redox system in mitochondria. The potential ability of PQ to accept electrons from complex (I, II, III, IV) leads to rapid reaction with molecular oxygen to yield superoxide anion which can lead to the formation of more toxic reactive oxygen species, e.g., hydroxyl radical, often taken as the main toxicant. Lipid peroxidation due to PQ has been implicated in a number of deleterious effects such as increased membrane rigidity, osmotic fragility, decreased mitochondrial components, reduced mitochondrial survival and lipid fluidity. The biological effect of reactive oxygen species (ROS) is controlled by a wide spectrum of enzymatic and non-enzymatic defense mechanisms such as superoxide dismutas (SOD), catalase (CAT) and glutathione. According to this hypothesis, the chemical cascades lead to the reduction of PQ, which reacts quite rapidly with molecular oxygen to yield superoxide anion. The generation of free radicals and lipid peroxidation are the main factors that lead to mitochondrial damage.

Hepatoprotective role of captopril on paraquat induced hepatotoxicity.

Paraquat (PQ) is a highly toxic herbicide that is used in most of the countries without restriction. The cytotoxic effect of PQ is mediated by radicals, which are the products of PQ reduction in cells. The anti-oxidative action of captopril, an angiotensin-converting enzyme inhibitor, appears to be through its ability to scavenge reactive oxygen species. In this study, the heptoprotective effect of captopril against PQ-induced hepatotoxicity was evaluated using primary cultured rat hepatocytes. Hepatocytes were isolated from male Wistar rats using a two-step collagenase perfusion, following incubation in the presence of captopril at 0.1, 0.2, 0.4 and 0.8 mM with or without PQ (5 mM). Hepatoprotective effects of captopril were studied indicating glutathione level intensity, thiobarbituric acid reactive substances (TBARs) formation, lactate dehydrogenase (LDH) leakage and cell viability every 70 min for 210 min. Captopril at 0.2 mM concentration maintained the LDH leakage, glutathione level and cell viability in the presence of 5 mM PQ. In spite of a significant elevation in TBARs formation in the PQ group, captopril did not show any significant protection. In conclusion, our data reveals that incubation of freshly isolated rat hepa-tocytes with captopril (0.2 mM) significantly protected the hepatocytes against the cytotoxicity of PQ (P < 0.05).

Captopril ameliorates toxicity induced by paraquat in mitochondria isolated from the rat liver.

The aim of the present study was to show the abilities of captopril as a thiol ACEi (angiotensin converting enzyme inhibitor), on mitochondria toxicity due to paraquat. Mitochondrial isolation from rat liver was divided into 4 groups. Group 1 was considered as control, group 2 received paraquat (5 mM), group 3 received captopril (0.08 mM) and group 4 received paraquat (5 mM)+captopril (0.08 mM). Lipid peroxidation, catalase activity, GSH (reduced glutathione) and GSSG (oxidized glutathione) concentrations were determined in isolated rat liver mitochondria. Simultaneous treatment of mitochondria with captopril (0.08 mM)+paraquat (5 mM) significantly ameliorate the mitochondria toxicity induced by paraquat (5 mM) alone. The results confirm antioxidant effect of captopril. This effect appears to be attributable to the Sulfhydryl Groups (SH) in the compound which may be due to captopril abilities to scavenge reactive oxygen species. The results indicate that captopril may prevent oxidative stress induced by paraquat.

Protective effect of melatonin against multistress condition induced lipid peroxidation via measurement of gastric mucosal lesion and plasma malondialdehyde levels in rats.

AIM: To study the protective effect of a natural antioxidant, melatonin, against multistress condition induced lipid peroxidation via determination of gastric damage and plasma malondialdehyde (MDA) level by high performance liquid chromatography in rats. METHODS: We compared indomethacin-induced gastric damage and MDA plasma level in three groups of rats: unoperated, bile duct ligated and sham-operated and evaluated the role of the melatonin on gastric damage and plasma MDA level. Indomethacin and melatonin were injected intraperitoneally in doses of 50 mg/kg and 20 mg/kg, respectively. Animals were killed 4 h after indomethacin injection. RESULTS: Indomethacin induced more severe gastric damage and plasma MDA level in bile duct ligated animals was significantly higher (3.1 +/- 0.04 micromol/L) than sham (2.8 +/- 0.04 micromol/L) and unoperated animals (1.4 +/- 0.08 micromol/L). Pretreatment with melatonin reduced indomethacin-induced gastric damage and plasma MDA level. CONCLUSION: Considering the results of this study, we suggest that in multistress conditions the intensity of gastric damage and the plasma MDA level are great and melatonin reduces the negative effect of lipid peroxidation and cell damage by oxidative stress in multistress conditions due to its antioxidizing activity.

Using Janus green B to study paraquat toxicity in rat liver mitochondria: role of ACE inhibitors (thiol and nonthiol ACEi).

Janus green B (JG-B) dye is used for vital staining of mitochondria and its reduction and oxidation shows the electron transfer chain alteration. The defect in electron transfer chain of mitochondria by paraquat is linked to free radical formation. In this present study we compared the abilities of different angiotensin-converting enzyme inhibitors, captopril (a thiol ACEi), enalapril, and lisinopril (two nonthiol ACEi) on mitochondria toxicity due to paraquat. The rat liver mitochondria were first isolated by centrifuge (at 4 degrees C at a speed of 7,000 g) in a mixture of 0.25 M saccharose solution and 0.05 M Tris buffer. Various concentrations of paraquat (1, 5, 10 mM), enalapril (0.25, 0.5, 1 mM), lisinopril (0.01, 0.05, 0.1 mM), and captopril (0.08, 0.1, 1 mM) on the mitochondria isolated from the liver with respect to time were investigated. Paraquat at a concentration of 5 mM was determined to be significantly different compared to control values (P<0.05) and captopril at a concentration of 0.08 mM, lisinopril (0.01 mM), and enalapril (0.25 mM) were found not to be significantly different from controls as found by spectroscopy at wavelength of 607 nm. Simultaneous treatment of mitochondria with captopril (0.08 mM) and paraquat (5 mM) significantly ameliorates the mitochondria toxicity of paraquat (5 mM) alone (P<0.05). Our results show that captopril is a more effective antioxidant than the nonthiol ACEi. Lisinopril (0.01 mM) and enalapril (0.25 mM) did not significantly change the mitochondrial toxicity by paraquat (5 mM) (P>0.05). The antioxidative action of captopril appears to be attributable to the sulfahydryl group (SH) in the compound. This effect may be due to captopril's abilities to scavenge reactive oxygen species.

Heavy metals (Ni, Cr, Cu) in the Karoon waterway river, Iran.

Environmental pollution is a world-wide problem, heavy metals belonging to the most important pollutants. The progress of industries has led to increased emission of pollutants into ecosystems. Karoon is the biggest and only navigable river in the South of Iran. Along the Karoon industrial units such as piping, steel, paint making, agriculture, paper mill, fish cultivation, abbottiors, electroplating industries drain their wastewater into the river. In this study, the concentrations of heavy metals (Ni, Cr, Cu) in the Karoon river have been determined. Samples were collected from 16 stations along the river, in winter and spring 1996. Heavy metal concentrations were measured by graphite furnace atomic absorption spectrometry. The minimal and maximal concentrations of these metals in winter were 69.3-110.7, 1.7-118.3, and 5.5-70.3 microg/l, for Ni, Cr, and Cu, respectively. The minimal and maximal concentrations of these metals in spring were 41.0-60.7, 0.7-19.8, and 0.5-28.7 microg/l, for Ni, Cr, and Cu, respectively. The results show that the pollution has increased along the river, down to the estuary at the Persian Gulf.

The bacterial endotoxin lipopolysaccharide enhances seizure susceptibility in mice: involvement of proinflammatory factors: nitric oxide and prostaglandins.

Central nervous system (CNS) inflammation in cases such as head trauma, infection and stroke has been associated with the occurrence of epileptic seizures. Microglia, the principal immune cells in the brain, readily become activated in response to injury, infection or inflammation. The bacterial endotoxin lipopolysaccharide (LPS) induces the activation of microglia and the production of proinflammatory factors including nitric oxide (NO) and prostaglandins (PGs). We examined the effect of LPS on seizure susceptibility of mice, by using the sensitive test, threshold of clonic seizures induced by i.v. infusion of pentylenetetrazole. LPS decreased the seizure threshold in a dose- and time-dependent manner. Pretreatment of mice with the NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester or cyclooxygenase inhibitor, piroxicam or the opioid receptor antagonist, (-)-naloxone completely reversed the proconvulsant effect of LPS. These results indicate that NO, PGs and endogenous opioid peptides seem to be involved in LPS-induced decrease in seizure threshold.

Survey of the natural occurrence of zearalenone in maize from northern Iran by thin-layer chromatography densitometry.

During September 2000, forty samples of preharvest maize from the province of Mazandaran, north Iran, were randomly collected. Samples were analysed for zearalenone (ZEA) by a thin-layer chromatography (TLC) method (AOAC Official Method). ZEA was extracted with chloroform, purified through a chromatographic column containing silica gel, separated on a TLC plate and quantified by densitometry. The analytical method was validated and was adequately reliable and sensitive. The mean recovery rate of ZEA from spiked samples was 92%. The absolute amount of ZEA standard detectable on a TLC plate was 20 ng, giving a limit of detection (LOD) of 100 ng g(-1). In some samples, it was shown that aflatoxins interfere with ZEA. Therefore, to remove this interference, the TLC mobile phase was changed. Data revealed that three of 40 (7.5%) maize samples contained ZEA in the range 100-212 ng g(-1), with a mean of 141+/-51 ng g(-1). This study, which is the first report of ZEA occurrence in Iranian maize, showed that the ZEA level in maize of Mazandaran province was lower than maximum limit for this mycotoxin in Iran.

In vitro inhibitory effects of antioxidants on cytotoxicity of T-2 toxin.

T-2 toxin is a secondary fungal metabolite produced by various species of Fusarium. It is capable of killing cells by causing extensive damage to the cellular membrane. In this study, cytotoxicity of T-2 toxin in combination with different antioxidant materials, including vitamin C (vit. C), vitamin E (vit. E) and selenium (sel) was investigated in vitro using the neutral red cytotoxicity assay. Eleven primary and transformed cell lines established from different tissues were used in pre-test experiments to identify the most sensitive and resistant lines by measuring the half lethal concentration (LC(50)) of the toxin. Three cell lines including human gingival fibroblast (HGF), the most sensitive (LC(50)=0.25 ng/ml), human colorectal adenocarcinoma (SW742), the most resistant (LC(50)=5.5 ng/ml) and human hepatoma (HepG2), with median susceptibility (LC(50)=2 ng/ml) were selected to investigate the inhibitory effects of the antioxidant agents, on cytotoxicity of T-2 toxin. Our results demonstrated that co-incubation of cell lines with different concentrations of T-2 toxin and antioxidants decreased significantly, but did not totally inhibit, the cytotoxicity of T-2 toxin (P<0.001). These findings suggest that in addition to lipid peroxidation, which is inhibited by antioxidants, other unidentified mechanism(s) seem to be involved in cytotoxicity of T-2 toxin.

Increase by NO synthase inhibitor of lead-induced release of N-acetyl-beta-D-glucosaminidase from perfused rat kidney.

Urinary N-acetyl-beta-D-glucosaminidase (NAG) had been shown to be a useful early marker of renal injury such as lead nephrotoxicity. This study investigated the effect of lead acetate on nephrotoxicity and its correlation with the nitric oxide (NO) system by determining the NAG release in perfused rat kidney. Lead acetate caused a time and concentration-dependent increase in enzymuria. The effect of concurrent perfusion with lead and L-arginine (L-arg) or L-N(G)-nitro arginine methyl ester (L-NAME) [substrate and inhibitor of NO synthase respectively] in the perfusion fluid was also studied by measuring NAG activity in the perfusate kidney rat. L-arg (2 mM) has significantly decreased the lead-induced NAG release (P < 0.001), and L-NAME (0.1 mM) has significantly increased the lead-induced enzyme release in a time-dependent manner (P < 0.001). Moreover, histological studies using light microscope showed that some of the epithelial cells of the proximal convoluted tubules are degenerated or necrotic and desquamated into the lumens in rat treated with lead acetate. This change occurs at 50 microg/dl of lead acetate and was increased by addition of L-NAME to lead acetate. However, addition of L-arg had no effect on histology of lead nephrotoxicity. This may suggest that lead may interfere with the NO system in rat kidney.