Dose-Dependent Effect of Short-Term Repeated Exposure to Amitraz on Some Reproductive Parameters in Male Albino Rats

Introduction

A pesticide is any substance or mixture of substances intended for preventing, destroying or controlling any pest, including vectors of human or animal disease, unwanted species of plants or animals causing harm during or otherwise interfering with the production processing, storage, transport or marketing of food, agricultural commodities, wood and wood products or animal feedstuffs, or substances which may be administered to animals for the control of insects, Dose-Dependent Effect of Short-Term Repeated Exposure to Amitraz on Some Reproductive Parameters in Male Albino Rats arachnids or other pests in or on their bodies [1]. They are widely used for preservation across the world.

Over the past years, estrogenic activities of pesticides have been the focus of research. However, not much attention has been paid to anti-androgenic effects of the pesticides for the observed degeneration in male reproductive health. This is the aim of this study; to determine their effects on male reproductive system.

Ann Adv Biomed Sci

Amitraz is one of the commonest pesticides used my man. Amitraz [N-methylbis (2,4-xylyliminomethyl) amine] is an insecticide of the formamidine group, initially synthesized in England in 1969, that is used as an acaricide and tickic albino ide in Veterinary medicine [2]. Its varied uses include treatment and control of generalized demodicosis in canines, ticks and mites on cattle and sheep, psylla infection of pears and also for control of red spider mites on fruit crop [3]. The formulations available for commercial use contain 12.5– 50% of Amitraz in an organic solvent like xylene and it is an effective treatment of feline scabies and demodicosis [4] is a very popular product, cheap and readily available, [5] and it is diluted with water before use [6].

In mammals, the main mechanism of action consists of activation of alpha 2- adrenoceptors similar to the mechanism of action of xylazine and clonidine, agonist alpha 2-adrenergics, and in the inhibition of the enzyme monoaminoxidase (MAO) [7].

Amitraz is rapidly and well absorbed after oral administration and eliminated from most of the tissues within few days. Amitraz is rapidly metabolized and excreted, mainly formamidine and 2, 4, dimethyl formanilide. These metabolites still contain the 2, 4 dimethylaniline (2,4DMA) moiety. The end product is 4- amino-3-methylbenzoic acid which is rapidly conjugated and excreted. This metabolic pattern is qualitatively similar in the rat, mouse, cat, dog, boboon, cow and human. In urine of these species 4-amino-3- methylbenzoic acid (free and conjugated form) is most predominant (>70%). Other metabolites like N- (2,4dimethylpheny1) N-methyl1 formamidine and 2,4, dimethyl formanilide constitute not more than 10% each.

Oral LD50 of Amitraz in the rats is the acute oral medical lethal dose for the rats which is 523- 800mg/kg body weight and the LC50 (6 hours) is 65mg/L of air [8, 9]. LD50 (Lethal Dose) of Amitraz is the dose which when administered to the rats will cause the death of half the population. LC50 (Lethal Concentration) of Amitraz is the concentration of the pesticide in air or water that will cause the death of half the population of the rats.

According to Amitraz Risk Characterization Document Volume 1 released by the Department of Pesticide Regulation (DPR), Carlifornia Environmental Protection Agency on December 12, 1995, a DPR review of the toxicology studies on the effects of Amitraz had identified adverse responses in human and animal studies.

Amitraz exerts toxic effects on ectoparasites by interaction with the octopamine receptors of arthropods. Although mammals do not have octopamine receptors, Amitraz exerts side effects in mammals through activation of α-2-adrenoceptors [10]. It is classified as a Group C possible human carcinogen [11].

Evidence from animal studies suggests that Amitraz is a potential reproductive toxicant. Moreover, Amitraz exhibits toxic effects in the human reproduction cells in vitro and inhibits the production of the steroid hormone progesterone [12].

Amitraz has been shown to induce cytochrome P450- dependent monooxygenases in the liver of treated rats and decrease hepatic glutathione activity in mouse [13, 14]. In bovine seminal vesicle, amitraz inhibited prostaglandin E2 synthesis. At high dose levels, amitraz can cause tumours in female mice. In dogs, following a topical application, amitraz increased plasma glucose and inhibited insulin secretion [10].

In humans, amitraz intoxication has been reported, and exposure effects include CNS depression, hypothermia, bradycardia, hypotension, hyperglycemia, glycosuria, vomiting and respiratory failure [15, 16].

Due to its excellent miticidal activity, amitraz is widely used in apiculture for the obligatory annual control of Varroa destructor. In beehives, amitraz is used in the form of smoke or vapour. This acaricide is easily hydrolyzed to toxic 2,4-dimethylaniline (2,4-DMA) and various products containing the 2,4- DMA moiety [17].

According to a DPR toxicology review, Central nervous system (CNS) effects in humans and dogs have been detected within hours of amitraz exposure. The effects seen in humans included paleness, dry mouth, drowsiness, disorientation, light headed feeling, slurred speech, and loss of consciousness. Toxic effects associated with subchronic exposure were indicated in a variety of studies. The most prevalent effects included decreases in body weight gain and abnormal CNS responses. The toxic effects of chronic exposure to amitraz included CNS depression, depressed growth rate, a reduction in food intake, hyperplastic nodules, and hyperkeratosis of the forestomach. Chronic exposure to amitraz has also been associated with oncogenicity [18].

Exposure to amitraz would be expected to pose a greater hazard to pet owners, agricultural workers and beekeepers because of the continual exposure to this acaricide. Therefore, it is very important to evaluate possible reproductive effects of amitraz in view of health protection [18].

Method

Twenty male rats obtained at the age of 2 weeks old and kept in the laboratory for a period of 14 days to acclimatize to the new environment. Animals were well fed with rat feeds and given access to water and hygienic environment throughout the duration of experiment.

When the rats attained an average weight of 160g they were the randomly assigned into groups consisting of five rats each. The LD 50 of Amitraz was 800mg/kg

Discussion

Results show that short term repeated oral administration of Amitraz caused reproductive toxicity in dose-dependent manner. This was evident with the decreasing sperm motility and sperm concentration from group 1 to group 4. This may imply that exposure to Amitraz affects the interstitial cells of Leydig that are responsible for the production of testosterone. Results also showed increase in the number of abnormal sperm cells (morphology) in dose-dependent manner as show in table 4. This agrees with a previous work in which it was documented that chlorimeform, a formamididine insecticide caused decrease in testosterone concentration resulting in infertility. It was also reported that a log time administration of Amitraz caused infertility [24].

Semen toxicity was also evident with decreasing serum concentration of sperm cells from low to high doses of Amitraz (Table 3).

There was also suppression of body and organ weights as observed in table 1and 2. These are also general responses to toxicity [27, 28].

There were clinical signs such as increased nasal discharge and nervousness that may have resulted from exposure to alpha-2-adreergic effect of Amitraz, while other clinical sigs such as reddish tear, fur staining, and dull fur suggest stress as a result of exposure to the test chemical [29, 30].

Conclusion

Short-term repeated exposure to Amitraz toxic to the body, and particularly the reproductive system and could therefore cause infertility in male. Therefore, male working in such companies that produce or apply Amitraz must take extra and deliberate precaution to reducing exposure.