Toxicity of endosulfan and manganese chloride: cumulative toxicity rating

There has been, in general, no accepted comparable way to express the effects of repeated doses. This study was designed to provide information on cumulative toxicity of manganese chloride (MnCl₂), endosulfan, and a mixture of these compounds and to suggest cumulative toxicity rating. Male mice were given the test compound i.p. 6 $\text{days}\text{week}$ for a minimum of 10 weeks and until the cumulative LD₅₀ remained constant for 3 consecutive weeks. Using a ratio between a single dose and weekly cumulative LD₅₀ (CLD₅₀), cumulative toxic factors (CTF) were determined. The CTF for weeks 1—13 for MnCl₂ ranged from 0 to 3.48; endosulfan 1.30 to 2.46, and 1.03 to 3.34 for a mixture of MnCl₂ and endosulfan. The observed LD₅₀ and CLD₅₀ values for a mixture of MnCl₂ and endosulfan were higher than the expected values, indicating a greatly reduced toxicity of a mixture, when given either in a single dose or repeated doses. Using the CLD₅₀ criterion as laid down in this study, the cumulative toxicity rating, class 1 to 6, has been suggested so as to have a comparative assessment of the cumulative potential of several compounds.     

The influence of carbaryl on the uptake of (3H)-noradrenaline (3H)-NA by rat hypothalamic slices

The uptake of (³H)-NA by rat hypothalamic slices was investigated following carbaryl poisoning. The insecticide was administered to rats orally in a single dose of 50% LD₅₀ and of 20% LD₅₀, and in repeated dosing for 14 days (5% LD₅₀ daily). The kinetics of (³H)-NA uptake was defined by the modified Lineweaver-Burk plots (Rmax was used instead of V_max and K_m was replaced with t05 max). The results indicated that in all the experiments carbaryl elevated the (³H)-NA uptake by hypothalamic slices in a dosage dependent fashion (insignificantly at the 20% LD₅₀ dose level,p >0.05) as evidenced by the increased R_max values. However, carbaryl simultaneously decreased the kinetics of the process in the hypothalamus since t_0.5max values were enhanced (insignificantly at the 5% LD₅₀ dose level,p >0.05). Carbaryl produced a dosedependent increase of t_0.5max values. The changes in the (³H)-NA uptake may be related to the increase of NA level in the hypothalamus following exposure to carbaryl observed by other authors.     

Acute behavioral toxicity of carbaryl and propoxur in adults rats

Motor activity and neuromotor function were examined in adult CD rats exposed to either carbaryl or propoxur, and behavioral effects were compared with the time course of cholinesterase inhibition. Rars received an IP injection of either 0, 2, 4, 6 or 8 mg/kg propoxur or 0, 4, 8, 16 or 28 mg/kg carbaryl in corn oil 20 min before testing. All doses of propoxur reduced 2 hr activity in a figure-eight maze, and crossovers and rears in an open field. For carbaryl, dosages of 8, 16 and 28 mg/kg decreased maze activity whereas 16 and 28 mg/kg reduced open field activity. In order to determine the time course of effects, rats received a single IP injection of either corn oil, 2 mg/kg propoxur or 16 mg/kg carbaryl, and were tested for 5 min in a figure-eight maze either 15, 30, 60, 120 or 240 min post-injection. Immediately after testing, animals were sacrificed and total cholinesterase was measured. Maximum effects of propoxur and carbaryl on blood and brain cholinesterase and motor activity were seen within 15 min. Maze activity had returned to control levels within 30 and 60 min whereas cholinesterase levels remained depressed for 120 and 240 min for propoxur and carbaryl, respectively. These results indicate that both carbamates decrease motor activity, but behavioral recovery occurs prior to that of cholinesterase following acute exposure.     

Approximate lethal dose versus median lethal dose in acute toxicity testing of pharmaceuticals

The relation between approximate lethal doses (ALD, i. e. the lowest dose at which mortality occurs) and the corresponding median lethal doses (LD₅₀) was investigated in 231 acute toxicity studies in mice and rats. The ALD values were divided into four classes (<5 mg/kg, 5–50 mg/kg, 50–500 mg/kg, 500–2000 mg/kg) and the LD₅₀/ALD factors were calculated. In intravenous studies the LD₅₀ values were higher than the ALD values by mean factors of 1.27–1.61 in mice and 1.25–2.84 in rats. In oral studies the LD₅₀ values were higher by mean factors of 1.46–2.5 in mice and 1.59–2.1 in rats. Only in 20 cases (8.7%) did the LD₅₀ values differ by factors higher than 2.     

Cytogenetic and hematological alterations induced by acute oral exposure of imidacloprid in female mice

Imidacloprid (IMD), 1(6-chloro-3-pyridinyl)methyl)-N-nitro-2-imidazolidinimine, was administered in female mice to study in vivo cytogenetic (chromosomal aberrations (CAs) and micronucleus assay) and hematological effects. The acute oral LD₅₀ was determined to be 150?mg/kg bw in mice following OECD guidelines using AOT StatPgm425 software. The mice were administered orally with distilled water (negative control); mitomycin C (MMC), 1?mg/kg (positive control) and sub-lethal doses of 37.5 (low), 75.0 (medium) and 112.5 (high) mg/kg bw (25%, 50% and 75% of LD₅₀) of IMD to analyze CAs and hematological effects after 24?h, whereas micronucleus test (MT) after 48?h. The genotoxicity analysis revealed that selected test doses of IMD – medium and high doses – induced significantly mitotic inhibition (p?<?0.01), CAs (p?<?0.01) and at high dose micronucleus (MN) formation (p?<?0.05). Significant changes in red blood cell (RBC; p?<?0.01), hemoglobin (Hb; p?<?0.01) and erythrocyte sedimentation rate (ESR; p?<?0.001) were observed, except WBC in which significant increase (p?<?0.001) was observed. Present observation substantiates overall significant dose dependent genotoxic potential (p?<?0.05; r?=?0.98) of IMD. Precautions should be taken to minimize possible risk to exposed farmers of the state of Haryana (India) – an agrarian economy.     

Structure-acute toxicity relationship of aromatic hydrocarbons in mice

The structure-acute toxicity relationship of aromatic hydrocarbons was examined in mice. In all test compounds, the acute toxicity was determined under 2 conditions: control LD₅₀ (LD₅₀-cont) and carbon tetrachloride (CCl₄)-pretreated LD₅₀ (LD₅₀-CCl₄). The CCl₄-pretreatment was done in order to evaluate the toxic potency of compound itself without the influence of metabolism. Both log (1/LD₅₀-cont) and log (1/LD₅₀-CCl₄) were functions of the log P, n-octanol/water partition coefficient, i.e., log (1/LD₅₀-cont) = 0.080 log P − 1.532 and log (1/LD₅₀-CCl₄) = −0.040(log P)² + 0.157 log P − 1.373. Both equations were statistically significant (P < 0.01). The ratio of LD₅₀-cont/LD₅₀-CCl₄ indicated that metabolic activation is more evident in hydrophobic compounds than in hydrophilic compounds. The results suggest that hydrophobicity of the aromatic hydrocarbons plays an important role in determining their acute toxicity.     

Dose-dependent effects of acute lindane treatment on Kupffer cell function assessed in the isolated perfused rat liver

1. Twenty-four hours after lindane exposure (5-60?mg/kg) a dose-dependent increase in the serum and hepatic levels of the insecticide was observed. Both the basal rate of O₂ consumption and the sinusoidal e ux of lactate dehydrogenase (LDH) by the perfused rat liver was enhanced after the administration of 20-60?mg lindane/kg. 2. The administration of low doses of lindane (5-20?mg/kg) increased carbon uptake and the carbon-induced O₂ consumption by the perfused liver, effects that were abolished by pretreatment with the Kupffer cell inactivator gadolinium chloride (GdCl₃). These parameters were not modified at the higher doses of lindane used (40-60?mg/kg). 3. In the dose range of 20-60?mg/lindane kg, carbon infusion led to a further increase inliver LDHe uxover values foundinits absence,aneffect that was markedly diminished by GdCl₃ in rat treated with 20?mg lindane/kg, being unaltered by GdCl₃ in animals given 60?mg/kg. 4. It is concluded that lindane induces a dose-dependent biphasic effect on Kupffer cell function, which could be conditioned by differential membrane perturbation actions of the insecticide that progressively accumulates in the liver, thus altering receptor-mediated and enzymatic processes related to colloidal carbon phagocytosis. Increased Kupffer cell function at low doses of lindane leads to enhanced liver injury. However, this feature of lindane intoxication at higher doses (60?mg/kg) is independent of Kupffer cell activity and seems to be determined by an oxidative stress mechanism induced at the parenchymal cell level.     

The influence of a wide range of dietary protein concentration on the acute oral toxicity of malathion

Summary Male albino rats were fed for 28 days from weaning on a diet containing 0% casein (group I), 3.5% casein (group II), 9% casein (group III), 26% casein (group IV), or 81% casein (group V). At the end of the dieting period, the LD₅₀±S. E. of malathion, in mg/kg body weight, was found to be 539±42 in group I, 599±138 in group II, 759±91 in group III, 1401±99 in group IV, and 649±51 in group V. The interval to death and the clinicopathologic signs of toxicity to malathion were essentially the same in all five dietary groups. The results were compared with corresponding available data on other pesticides including captan. carbaryl. diazinon, dicophane, endosulfan, lindane and on the herbicides chlorpropham and monuron. The toxicity of these agents was not markedly increased until dietary protein was reduced to less than one third of normal or optima intake. At levels of one seventh, or less, of normal dietary protein, toxicity of al agents was increased but to some (e.g. captan) much more than to others (e.g. malathion). The high casein diet of group V was toxic to albino rats when feeding was started at weaning but not if feeding was started 2–3 weeks after waning.This project was supported by Grant F5/181/5 of the World Health Organization.     

Changes in glutathione-redox balance induced by hexachlorocyclohexane and lindane in CHO-K1 cells

1. The basal cytotoxic effect of the organochlorine pesticides hexachlorocyclohexane and lindane on CHO-K1 cultures was assessed at fractions of their lethal doses as determined by the neutral red incorporation (NRI) assay (NRI_6.25, NRI_12.5 and NRI₂₅). The sulphur-redox cycle enzymes glutathione peroxidase, glutathione reductase and glutathione S-transferase, and total and oxidized glutathione were evaluated at several points during the standard growth curve of the cultures. 2. After incubation with each compound for 24h, both glutathione peroxidase and reductase showed a substantial increase at the lowest exposure doses (NRI_6.25) - more significantly for lindane than for 1,2,3,4,5,6-hexachlorocyclohexane (HCH) - and dropped at higher doses of both compounds. The reduced and oxidized glutathione content was greatly diminished at the lower exposures, whereas the total glutathione content was higher at NRI_12.5 values. 3. Changes in cell membrane integrity were assessed for a wide range of pesticide concentrations with the lactate dehydrogenase release assay and lipid peroxidation. Membrane leakage and peroxide production were significantly enhanced at concentrations of HCH 50µg ml^?1, although this effect was not significant at lindane concentrations <200µg ml^?1. 4. Lipid peroxidation increased with exposure to HCH at concentrations as low as NRI_6.25, whereas in the case of lindane, this increase was only significant at doses of NRI₂₅ and above.     

Effect of methanol on endogenous and exogenous carnitine levels in rat plasma

The effect of methanol on the levels of endogenous carnitine and its derivatives was studied in male Sprague-Dawley rats aged three months. In addition, the effect of L-carnitine supplementation on metabolic disturbances caused by methanol intoxication was studied. The rats were randomized into six groups, including two control groups. Methanol was given at 1/4 LD₅₀ and 1/2 LD₅₀/kg b.w. (or water in control) through an intragastric tube, and L-carnitine (or 0.9% NaCl in the control) was injected intraperitoneally. The levels of plasma L-carnitine and its derivatives were measured at selected time points for four days. Following methanol administration, the rats exhibited dose-dependent increases in L-carnitine levels and altered ratios of L-carnitine and its derivatives. L-carnitine supplementation accelerated the normalization of metabolic disturbances, as indicated by the acylcarnitine to free carnitine ratio (AC/FC). The protective effect of L-carnitine is supported by the fact that 100% of the methanol-treated rats supplemented with carnitine survived, while 8/60 rats and 27/101 rats died at methanol doses of 1/4 LD₅₀ and 1/2 LD₅₀, respectively, in groups without L-carnitine supplementation.     

Evaluation of cytotoxicity and genotoxicity of pesticide mixtures on lymphocytes

The cytotoxicity and genotoxicity of pesticide mixtures viz. endosulfan?+?chlorpyrifos, chlorpyrifos?+?profenofos, and endosulfan?+?profenofos were evaluated on cultured human peripheral blood lymphocytes using assays for cell viability, and genotoxicity using chromosomal aberrations test and comet assay. The LC₅₀ values for cytotoxicity were 3.50?μM, 4.18?μM, and 10.5?μM for profenofos, endosulfan, and chlorpyrifos respectively. When combined in equimolar concentrations, the LC₅₀ values for cytotoxicity were 1.4?μM, 1.8?μM, and 2.0?μM for endosulfan?+?chlorpyrifos, chlorpyrifos?+?profenofos, and endosulfan?+?profenofos, respectively. Higher concentrations of individual pesticides (0.5–4.0?μM) but very low concentrations of pesticide mixtures caused significant DNA damage. Additive index values indicated a synergistic effect of toxicity for endosulfan?+?chlorpyrifos combination (1.12 TTU). The binary mixture of chlorpyrifos?+?profenofos showed an additive toxicity (0.46 TTU) while an antagonistic effect was observed for endosulfan?+?profenofos combination. Synergism could be due to these complementary pesticides simultaneously acting in different ways, magnifying their efficacy, whereas an additive interaction would imply that the chemicals are acting by the same mechanism and at the same target. Analysis of toxicity of pesticide mixtures may serve as important biomarker for occupational and household exposure to pesticides, with different modes of action.     

A teratology study of carbaryl and malathion mixtures in rat

Recently, much controversy has developed in relation to the use of pesticides alone and in mixtures. Mixtures are used as a more efficient method of pest control. Carbaryl and malathion are one of many combinations used today. A limited amount of work has been done with these two pesticides in relation to their teratogenic potential. This study examined the teratological parameters of carbaryl and malathion in combination compared to the effect of the individual insecticides. Formulation grade carbaryl (0, 1, 10, and 100 mg/kg), formulation grade malathion (1 and 50 mg/kg), and a formulation grade mixture of carbaryl/malathion (1/1 and 50/50 mg/kg) were administered daily by gavage for 3 mo prior to and throughout gestation. Dams were sacrificed on d 20 of gestation, and the fetuses were examined for external, skeletal, and visceral malformations. Significant decreases in dam weight gain during pregnancy and a slight decrease in the number of implantations and number of live fetuses per dam were observed with the 100-mg/kg carbaryl group and were further reduced in both combination doses. The combination dose groups showed a significant reduction in placenta weight. No increases were seen in skeletal or visceral anomalies for the individual treatment groups; however, an increase in external hemorrhagic spots was observed with malathion at 50 mg/kg and the high-dosage mixture group.     

补骨脂素和异补骨脂素的急性毒性和相互作用

目的 探究补骨脂素、异补骨脂素的急性毒性及两者（1∶1）混合使用后的相互作用。方法 补骨脂素（1 125、843、633、475 mg/kg）、异补骨脂素（475、404、343、292 mg/kg）以及两者1∶1的混合物（633、538、457、389、330 mg/kg）1次性ig给予小鼠,连续观察并记录14 d小鼠的毒性反应和死亡情况,用SPSS计算补骨脂素、异补骨脂素以及两者混合使用后的半数致死量（LD₅₀）,用等效线图解法判断两者的相互作用。结果 给药组小鼠均出现僵直、腹部贴地、活动力减弱,甚至抽搐、口眼周有分泌物,心率减慢直至死亡的现象,与助溶剂组比较,体质量呈降低趋势;补骨脂素LD₅₀为638.69 mg/kg,95%可信限为526.91～785.78mg/kg;异补骨脂素LD₅₀为351.72 mg/kg,95%可信限为248.17～394.57 mg/kg;两者1∶1混合给药的LD₅₀为454.66 mg/kg,95%可信限为422.58～489.59;两者合用的LD₅₀在补骨脂素和异补骨脂素相加等效线上。结论 补骨脂素和异补骨脂素大剂量给予小鼠时,引起药物急性毒性反应,1∶1混合给药具有相加作用。     

Evaluation of the mutagenic potential of four commercial mixtures of insecticides

Male mice (Q strain) were given a single ip injection at the maximum tolerated dose of one of four commercial mixtures of insecticides: Luxan Tue-Taons (150 g dimethoate and 150 g fenitrothion/litre), Metadipterex (210 g trichlorfon and 270 g methyldemeton/litre), Dynafos (155 g malathion, 60 g dichlorvos and 75 g carbaryl/litre) and Phosan Plus (95 g dimethoate, 100 g malathion and 100 g methoxychlor/litre). At the maximum tolerated doses, Luxan Tue-Taons (60 mg/kg), Metadipterex (15 mg/kg), Dynafos (50 mg/kg) and Phosan Plus (100 mg/kg) did not induce chromosome aberrations in bone-marrow cells, spermatogonia or primary spermatocytes of the mice. No evidence of potential genetic effects was obtained in a dominant lethal mutation assay.     

A simple method for screening assessment of acute toxicity of chemicals

We proposed a simple method for screening assessment of acute oral and dermal toxicity using only three rats and mice of each sex at each dose level. Animals were first treated with chemicals at a dose of 2000 mg/kg and were carefully observed for compound-related morbidity and mortality. If none of the animals died, the following toxicity tests were suspended. If some of the animals died, toxicity tests at doses of 200 and 20 mg/kg were performed. The approximate LD₅₀ values calculated by this method showed little difference between two separate laboratories and were in good agreement with LD₅₀ values reported in the literature. Our toxicological data also showed that LD₅₀ values were about 2–2.5 times the MNLD (maximum non lethal dose) in acute oral and dermal toxicity. This meant that a chemical could be regarded as having an LD₅₀ of about 4000 mg/kg or higher when there was no mortality at the dose of 2000 mg/kg. A chemical with such low toxicity would not require further testing for lethal effects. Therefore, this simple method combining the fixed-dose procedure with the limit test is suitable for determination of approximate LD₅₀ values of chemicals and for screening for necessity for classical full LD₅₀ test using many animals.This work was supported by a grant from Ministry of Health and Welfare in Japan (No. 467 and 511)     

The joint toxic action of perchloroethylene with benzene or toluene in rats

The joint toxic action of mixtures of perchloroethylene with benzene or toluene was tested at five dose levels for each of six binary combinations with 20 rats per dose.LD₅₀ data with 95% fiducial limits are reported for each mixture and tests for additive joint toxicity were made. The results indicate that the mixtures of perchloroethylene and benzene gave values for the LD₅₀ which were slightly less than additive while perchloroethylene and toluene mixtures had LD₅₀ values which could not be predicted by an additive model.     

Increasing maneb doses induces reactive oxygen species overproduction and nephrotoxicity in adult mice

Background and purpose: The aim of this study was to elucidate the biochemical, molecular and histopathological aspects of the kidney injuries as well as the hematological perturbations induced after adult mice exposure to increasing doses of maneb (MB).

Material and method: Adult mice were intraperitoneally treated for seven days with four graded doses of MB, corresponding to 1/8, 1/6, 1/4 and 1/2 of its lethal dose (LD₅₀=1500?mg/kg body weight).

Results: Hematological analysis revealed a significant disruption in total white blood cells and platelets and a significant decrease in the plasmatic levels of ferrozine in mice treated with 1/8, 1/6 and 1/4 of MB LD₅₀. However, the ferrozine levels increased significantly in the group treated with 1/2 of MB LD₅₀. Evenly, our results showed a significant increase in the levels of malondialdehyde, lipid hydroperoxides, hydrogen peroxide and advanced oxidation protein products in all treated groups. The activities of catalase and glutathione peroxidase decreased significantly in all MB treated mice. Additionally, all treated groups exhibited strong nephrotoxicity signs, including increases in plasma urea, creatinine and albumin levels and lactate dehydrogenase activity, as well as a significant decrease in uric acid levels. Electrophoresis analysis revealed nucleic acid degradation, testifying the genotoxicity of MB. Moreover, the histopathological observations showed severe renal injuries, which could be related to the above mentioned data.

Conclusions: Our data showed, for the first time, that the MB tested doses led to oxidative stress installation causing renal cell damages and lowering all defense systems capacities.     

Toxicity of Jatropha curcas phorbol esters in mice

Phorbol esters are the main toxins in Jatropha curcas seed and oil. The aim of this study was to assess the acute toxicity of phorbol esters given by intragastric administration and to determine the LD₅₀ for Swiss Hauschka mice. The LD₅₀ and 95% confidence limits for male mice were 27.34 mg/kg body mass and 24.90–29.89 mg/kg body mass; and the LD₅ and LD₉₅ were 18.87 and 39.62 mg/kg body mass, respectively. The regression equations between the probits of mortalities (Y) and the log of doses (D) was Y = −9.67 + 10.21 log (D). Histopathological studies on the organs from the dead mice showed: (1) no significant abnormal changes in the organs at the lowest dose (21.26 mg/kg body mass) studied, (2) prominent lesions mainly found in lung and kidney, with diffused haemorrhages in lung, and glomerular sclerosis and atrophy in kidney at doses ?32.40 mg/kg body mass, and (3) multiple abruption of cardiac muscle fibres and anachromasis of cortical neurons at the highest dose of 36.00 mg/kg body mass. The results obtained would aid in developing safety measures for the Jatropha based biofuel industry and in exploiting the pharmaceutical and agricultural applications of phorbol esters.     

Tolerance to the carbamate insecticide propoxur

Male mice were given the carbamate insecticide propoxur (2-isopropoxyphenyl methylcarbamate; Baygon®) in drinking water at weekly increasing concentrations (from 50 to 2000 ppm), for a period of 6 weeks. At the end of the treatment the LD₅₀ for propoxur was significantly higher in the treated animals as compared with controls. Propoxur-treated animals were also resistant to the hypothermic effect of an acute administration of the same compound. Groups of mice were challenged with the cholinergic agonist carbachol at intervals during the drinking water dosing and at its end. No differences in sensitivity to carbachol acute toxicity were found between control and treated animals. Propoxur-tolerant animals were also not resistant to the hypothermic effect of oxotremorine, another cholinergic agonist. [³H]Quinuclidinyl benzilate ([³H]QNB) binding (a measure of muscarinic receptor density and affinity) in forebrain, hindbrain and ileum never differed in control and treated mice. The possibility that repeated administrations of propoxur induced increased metabolic inactivation was tested by measuring hexobarbital sleeping time and carboxylesterase activity in treated and control mice. No changes in tissue carboxylesterase activities occurre but hexobarbital sleeping time was significantly reduced in propoxur treated animals suggesting an induction of hepatic microsomal enzymes. These results suggest that tolerance to propoxur is not mediated by a decrease of cholinergic receptors, as reported for other acetylcholinesterase inhibitors, but possibly by an enhancement of its metabolism.     

The value of acute toxicity testing of pharmaceuticals for estimation of human response

The determination of single high doses of active pharmaceutical ingredients (API) is used mostly to fulfill regulatory demands. Oral LD₅₀ values in animals for over 300 API were compared to the minimal effective therapeutic doses (METD) in humans in order to find a correlation between animal and human data. The highest correlation between human METD and animal LD₅₀ was found for the dog (R = 0.323), the lowest for the rat (0.287). It was determined that acute oral LD₅₀ of rats have poor correlation with the METD, and cannot be used as a classification criteria into official acute toxic categories. Only 13% of API has been classified as fatal if swallowed according to the EU CLP regulation, none of the substances with very low therapeutic dose have been identified as EU CLP acute toxicity category 1. Substances with very low therapeutic doses, which could potentially have toxic effects in humans, are not identified with the use of oral LD₅₀ and current classification system. We propose that the acute toxicity based on rat LD₅₀ dose is not used as a basis for classification of pharmaceuticals, and that the METD is applied as basis for classification.