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In This Article
 »  Abstract
 »  Introduction
 »  Material and Methods
 »  Results
 »  Discussion
 »  References

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RESEARCH PAPER
Year : 2004  |  Volume : 36  |  Issue : 1  |  Page : 25-28
 

Single oral dose toxicity study of a-cypermethrin in rats


Department of Pharmacology, University College of Medicine, Calcutta University, Kolkata – 700020, India

Correspondence Address:
Department of Pharmacology, University College of Medicine, Calcutta University, Kolkata – 700020, India
skmv2@rediffmail.com

 » Abstract 

Objective: To evaluate the acute effect of a-cypermethrin (a-CP) on antioxidant activities, oxidants, biochemical and histopathological changes at LD50 dose level. Material and Methods: a-CP at single LD50 (145 mg/kg) dose was administered orally to Wistar rats while controls received an equal volume of the vehicle, DMSO. The antioxidants, oxidants, biochemical and histopathological changes in some visceral organs were studied following a-CP. Results: A single LD50 dose of a-CP increased the malondialdehyde (MDA) level and decreased the activities of catalase (CAT), superoxide dismutase (SOD) and glycogen in the liver. It also increased the serum aminotransaminases (AST, ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) activities, and blood glucose level. It produced some cytotoxic effect on the lungs, liver, stomach, intestine, testes and cerebellum. The vehicle DMSO may have influenced the determination of LD50 of a-CP in rats. Conclusion: A single, oral LD50 dose of a-CP decreased antioxidant status, and altered biochemical parameters, which correlated with histopathological changes in rats.

How to cite this article:
Manna S, Bhattacharyya D, Basak D K, Mandal T K. Single oral dose toxicity study of a-cypermethrin in rats. Indian J Pharmacol 2004;36:25-8


How to cite this URL:
Manna S, Bhattacharyya D, Basak D K, Mandal T K. Single oral dose toxicity study of a-cypermethrin in rats. Indian J Pharmacol [serial online] 2004 [cited 2020 Aug 4];36:25-8. Available from: http://www.ijp-online.com/text.asp?2004/36/1/25/6788



 » Introduction Top


Cypermethrin is a synthetic pyrethroid with potent insecticidal property. The technical grade cypermethrin is the racemic mixture of 8 isomers (four cis and four trans isomers). Two stereoisomers are termed a-isomer of cypermethrin, which is believed to be the most active isomer, and is known as a-cypermethrin.[1] Alfa-cypermethrin (a-CP) is extensively used not only as an ectoparasiticide in animals, but also in agriculture and public health programs. Some of the toxic actions of a-CP have been reported earlier,[1] but the effects of oral administration of a-CP on blood biochemistry and histology of some tissues in rats have not been studied. It has been reported[1] that the vehicle used for a-CP has a great influence on the LD50, probably by influencing absorption. The oral LD50 values in rats were 79 mg/kg (5% in corn oil)[1] and 40-80 mg/kg (10% in corn oil).[1] But the LD50 value of a-CP for rats with dimethylsulfoxide (DMSO) as a vehicle has not been studied. Therefore, the present study was undertaken to determine the oral LD50 of a-CP in DMSO and to know the acute effect of a-CP on the antioxidant status, biochemical parameters and histopathology of the lung, liver, stomach, kidney, testis and cerebellum following a single dose in rats.


 » Material and Methods Top

Pesticide
Alfa-cypermethrin (a-CP, >99% pure, Gharda Chemicals Ltd. Mumbai).

Animals and experimental design
Ninety healthy adult Wistar rats of both sexes (equal sex ratio; weighing about 200 g) were divided into nine equal groups (I to IX) each consisting of ten animals. All rats were kept under controlled conditions of temperature (22±10C) and humidity (60±5%). They were given pellet food (Amrut feeds Ltd., Pune, India) and drinking water ad libitum. A twelve-hour day and night cycle was maintained in the animal house. The experimental protocol met the national guidelines on the proper care and use of animals in laboratory research. The Institutional animal ethics committee approved the experimental protocol.

Groups I - VI were used for the determination of LD50 of a-CP. Group VII served as control group for LD50 determination and Group VIII was used as an experimental group for biochemical, antioxidants and histopathological study. Group IX served as control for Group VIII. The animals were fasted overnight and a-CP was administered orally by gavage after dissolving in DMSO (1 ml) as stated above. The animals were observed for respiratory and CNS symptoms, behavioral patterns and mortality. The LD50 was determined by graphical method.[2] a-CP was administered orally to the animals of Group VIII at 145 mg/kg and Group IX animals were dosed an equal volume of DMSO only (1 ml). The control group for LD50 determination (Group VII) and the control group for study of a-CP-induced changes in different parameters (Group IX) are separate because they were experimented on different days.

Biochemical profile
Out of 10 animals in Group VIII (experimental), four animals died during the 48 h observation period. The remaining six animals of Group VIII and all the animals of Group IX were killed under ether anesthesia after 48 h of treatment and blood was collected after severing the neck vessels in two sets of test tubes. One set was kept under refrigeration (40C) for separation of serum and utilized for the estimation of aspartate transaminase (AST), alanine transaminase (ALT),[3] lactate dehydrogenase (LDH),[4] and alkaline phosphatase (ALP)[5] activities, total protein (TP),[6] globulin and albumin (GLB, ALB)[7] levels. The blood of another set of test tubes (with a mixture of potassium oxalate and sodium fluoride as anticoagulant) was used for estimation of glucose.[8] The liver was dissected out and washed in physiological saline. The liver homogenate was utilized for the estimation of catalase (CAT),[9] super oxide dismutase (SOD),[10] reduced glutathione (GSH),[11] malondialdehyde (MDA)[12] and glycogen.[13]

Histopathology
The lung, liver, stomach, kidney, testis and cerebellum were fixed in 10% neutral buffered formalin. Sections of 3-5 mm thickness were stained with hematoxylin and eosin (H&E) for histological examination.

Statistical analysis
All the values were expressed as mean±SEM. Statistical analysis was done using SPSS 7.5. The statistical significance of differences between the two means was assessed by unpaired Student's 't' test. A difference at P<0.05 was considered statistically significant.


 » Results Top


a-CP did not produce any gross effect on the central nervous system at 100 mg/kg. However, at higher doses ranging from 125 to 225 mg/kg, it produced signs of CNS stimulation followed by prolonged depression (for 20-24 h). Initially, the animals exhibited chewing, licking, salivation and then CNS depression. A somewhat variable sequence of motor symptoms then developed involving occasional pawing, or burrowing, coarse whole body tremor associated with movement of legs, gradual development of hind limb extensor tone and an increase in startle response. Finally, choreoathetosis (sinuous writhing) developed, and the animals exhibited slow twisting or writhing movement of the neck and tail. When the symptoms progressed, choreoathetosis became continuous and the righting reflex was gradually lost. Violent twisting movements sometimes lifted the body from the floor in severely affected animals and these were classed as severe athetosis. At the terminal stage, animals showed labored breathing, gasping and death. The data for the determination of LD50 were 100,125,150,175,200 and 225 mg/kg and the probit values were 3.04, 4.75, 5.25, 5.25, 6.28 and 6.96 respectively. The acute oral LD50 value was calculated as 145 mg/kg-body weight.

Biochemical profile
The effect of a-CP on certain biochemical parameters is summarized in [Table - 1]. a-CP significantly (P<0.05) increased the activities of serum AST, ALT, ALP and LDH. It decreased the activities of liver CAT, SOD and increased the MDA level, but non-significantly, and without appreciable change in the GSH level. The blood glucose level was significantly increased whereas liver glycogen was significantly decreased. Serum ALB, GLB and total protein levels were not appreciably altered.

Histopathology
It is evident that a-CP produced hemorrhages in the lungs [Figure - 1]. Congestion and hemorrhages were found in the liver [Figure - 2]. In the stomach it produced desquamation and necrosis of the epithelium [Figure - 3]. The section of testis revealed edema between seminiferous tubules, vacuolation and hyalinization in the tubules [Figure - 4]. Congestion and hemorrhages in the meninges [Figure:5] and cerebellum were observed. The postmortem findings of rats (died within 48 h) showed bloated stomach with hemorrhages in the stomach and intestine. Hemorrhages were also seen in the lungs. No other changes were discernible in other visceral organs.


 » Discussion Top


The pattern of the motor signs after a-CP administration is strongly suggestive of CNS toxicity. Animals showed a sequence of the signs of toxicity, and a sinuous writhing movement. The acute oral LD50 value of a-CP in DMSO was 145 mg/kg, which is higher than the LD50 value determined using other vehicles like corn oil. This suggests that the vehicle DMSO reduced the toxicity of a-CP in rats. Activities of SOD, CAT, GSH, and MDA levels in the liver reflect the oxidative status and the serum enzymes like AST, ALT, and ALP represent the functional status of the liver. Chemical-induced cellular alteration varies from simple increase of metabolism to death of cell. The increase or decrease of enzyme activity is related to the intensity of cellular damage. Therefore, increase of transaminase activity along with the decrease of activity of free radical scavengers may be the consequence of a-CP induced pathological changes of the liver. The severe hyperglycemia may be due to the effect of an increase in the catecholamines level, which causes glycogenolysis, and this may be the reason for a significant decrease in liver glycogen. The decreased CAT and SOD activities and increased MDA level in the liver as well as increased serum AST, ALT and ALP levels suggest that a-CP causes hepatic damage which may be through free radicals. a-CP undergoes metabolism in the liver via esoteric and oxidative pathways by the cytochrome P450 microsomal enzyme system14 which results in oxidative stress producing depletion of the activity of CAT, SOD, and the glycogen level, and increased level of MDA leading to hepatic necrosis. Blood lactate was not measured in this study, but increased activity of LDH may indicate a shift towards anaerobiosis resulting in enhanced production of lactic acid, which may be a cause for the convulsions. The antioxidant status and biochemical changes correlated with histopathological changes of tissues are in agreement with the study by Giray et al.[15] In conclusion, the present study demonstrated that oral LD50 of a-CP dissolved in DMSO in rats was 145 mg/kg. In acute toxicity study, single dose oral LD50 of a-CP in rats increased the levels of liver MDA, and serum AST, ALT, ALP, LDH, glucose and decreased the activities of SOD and CAT and the glycogen level. It produced moderate cytotoxic effects in the lungs, liver, testis and the least effect in the cerebellum, stomach and intestine. The pathological changes correlated with the altered enzyme activities. 

 » References Top

1.World Health Organization (Geneva). Alfa-cypermethrin. In:Environmental Health Criteria-142, WHO. Geneva: Library cataloguing in publication data; 1992. p. 20-43.  Back to cited text no. 1    
2.Miller LC, Tainter ML. Graphical method for determination of LD50. Proc Soc Exp Biol Med 1944;54:261-71.   Back to cited text no. 2    
3.Reitman S, Frankel SA. Colorimetric method for the determination of glutamic oxaloacetic and glutamic pyruvic transaminase. Am J Clin Patho 1957;28:56-63.  Back to cited text no. 3    
4.Bergmeyer HU, Bernt E, Hess B. Lactate dehydrogenase, in method of Enzymatic Analysis. Bergmeyer HU, editor. London: Academic Press; 1974. p. 735.  Back to cited text no. 4    
5.King EJ, Armstrong AR. In vitro determination of alkaline phosphatase. Canad Med Ass J 1934;31:376-9.  Back to cited text no. 5    
6.Doumas BT, Waston WA, Biggs AG. Biuret method for quantitative estimation of total protein in serum or plasma. Clin Chem Acta 1971;31:87-91.  Back to cited text no. 6    
7.Rodkey FL. Direct spectrophotometric determination of albumin in human serum. Clinical Chemistry 1965;11:478-9.  Back to cited text no. 7    
8.Trinder P. In vitro enzymatic colorimetric method for the estimation of glucose in serum/plasma. Ann Clin Biochem 1969;6:24-8.  Back to cited text no. 8    
9.Lick H. Catalase in: "Methods of Enzymatic Analysis". Bergemeuer HU, editor. 3rd ed. Verlag Chemie. New York: Academic press; 1963. p. 885-8.  Back to cited text no. 9    
10.Misra HP, Fridovich I. The role of superoxide anion in the antioxidation of epinephrine and a simple assay for superoxide dismutase. J Biol Chem 1972;247:3170-5.  Back to cited text no. 10    
11.Grifith OW. Determination of glutathione and glutathione disulphide using glutathione reductase and 2- vinylpyridine. Anal Biochem 1980;106:207-12.  Back to cited text no. 11    
12.Placer ZA, Cushman LL, Jhonson BC. Estimation of product of Lipid peroxidation (Malonyl dialdehyde) in biochemical system. Anal Biochem 1966;16:359-64.  Back to cited text no. 12    
13.Montgomery R. Determination of glycogen. Arch Biochem Biophy 1967;67:378-86.  Back to cited text no. 13    
14.Floodstrom S, Warngard L, Lijunquist S, Ahlborg UG. Inhibition of metabolic cooperation in vitro and enhanced enzyme altered foci incidence in rat liver by the pyrethroid insecticide fenvelerate. Arch Toxicol 1988;61:218-23.  Back to cited text no. 14    
15.Giray B, Gurbay A, Hineal F. Cypermethrin induced oxidative stress in rat brain and liver is prevented by vit-E or allopurinol. Toxicol Lett 2001;118:139-46.  Back to cited text no. 15    
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