Metabolism of organophosphorus insecticides. XI. Metabolic fate of dimethoate in the rat

Acute exposure to organophosphorus pesticide metabolites compromises buffalo sperm function and impairs fertility

Agrichemicals such as organophosphorus pesticides' metabolites (OPPMs) are more hazardous and pervasive than their parent pesticides. Parental germline exposure to such xenobiotics leads to an elevated susceptibility towards reproductive failures e.g. sub- or in-fertility. This study sought to examine the effects of low-dose, acute OPPM exposure on mammalian sperm function using buffalo as the model organism. The buffalo spermatozoa were briefly (2 h) exposed to metabolites of the three most prevalent organophosphorus pesticides (OPPs) viz. Omethoate (from Dimethoate), paraoxon-methyl (from methyl/ethyl parathion) and 3, 5, 6-trichloro-2-pyridinol (from chlorpyrifos). Exposure to OPPMs resulted in compromised structural and functional integrity (dose-dependent) of the buffalo spermatozoa typified by elevated membrane damage, increased lipid peroxidation, precocious capacitation and tyrosine phosphorylation, perturbed mitochondrial activity and function and (P < 0.05). This led to a decline in the in vitro fertilizing ability (P < 0.01) of the exposed spermatozoa, as indicated by reduced cleavage and blastocyst formation rates. Preliminary data indicate that acute exposure to OPPMs, akin to their parent pesticides, induces biomolecular and physiological changes in spermatozoa that compromise their health and function ultimately affecting their fertility. This is the first study demonstrating the in vitro spermatotoxic effects of multiple OPPMs on male gamete functional integrity.

Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005 μg g^-1 for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050 μgg^-1 fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400 g a.i h^-1 recorded initial deposits of 5.20 and 10.05 μg g^-1 and 0.33 and 0.48 μg g^-1 for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34 days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application. This article is protected by copyright. All rights reserved.

Dimethoate-induced biochemical and histopathological changes in the liver of rats

Dimethoate is an organophosphorus insecticide and acaricide used for the control of a wide range of insects, including houseflies and mites, on a variety of fruits, vegetables, field and forestry crops. The aim of the current study was to evaluate the subchronic toxicity of orally administered dimethoate in Wistar albino rats, based on the histopathological and biochemical findings in the liver. The animals of the exposed groups were fed with laboratory chow combined with 2, 8 or 20 mg/kg body weight/day dimethoate for 90 consecutive days under controlled laboratory conditions. At the end of the experiment, body weight gain, absolute and relative liver weights, liver cholinesterase activities and total protein levels were determined. Histopathological changes in the liver were also determined using a light microscope. Results showed that there were decreases in relative liver weights of exposed rats. Although liver total protein levels were significantly increased, liver cholinesterase activities were decreased in all exposed groups. Dimethoate caused dose-related histopathological changes such as mononuclear cell infiltration, congestion, an enlargement of the veins and sinusoids, hepatocellular damage, necrotic changes, an increase in the number of Kupffer cells, cytoplasmic vacuolization and degeneration in nuclei in the liver of exposed rats. These effects did not vary between the sexes.

Effect of different schedules and efficacy of progesterone on implantation in dimethoate treated albino mice

Dimethoate, an organophosphorus pesticide, was administered orally at a dose of 28mg/(kg body weight day) to nulliparous pregnant albino mice on day 3 only and for days 3, 5 and 7 to examine the possible mechanisms for the time dependent and efficacy of progesterone on implantation in dimethoate treated animals. Control mice received similar quantities of distilled water. Autopsy on day 8 revealed that the distilled water treated mice were pregnant and had a normal number of implantations and a normal duration of diestrus. Treatment with dimethoate on day 3 only and for days 3 pregnancy caused a partial inhibition of implantation wherein 6 and 4 out of 10 mice were pregnant with 68.04 and 83.69% pre-implantation loss, respectively. However, treatment with 28mg/(kg body weight day) dimethoate for days 5 and 7 caused complete inhibition of implantation in all the mice with 100% pre-implantation loss and the uterus showed no implantations. There was a significant decrease in the body weight, ovaries and uterine weights in 28mg/(kg body weight day) dimethoate treatment for days 7 of pregnancy in mice as there was complete inhibition of implantations. These groups exhibited an increase in the estrus phase. However, there was no significant change in the weight of other organs in dimethoate treated mice. Inhibition of implantation by dimethoate may be due to imbalance in the estrogen:progesterone ratio, essential for implantation. Based on this hypothesis 4, 9 and 12mg/(kg body weight day) progesterone was administered subcutaneously along with 28mg/(kg body weight day) of dimethoate for days 7 of pregnancy to counteract the effect of dimethoate and to maintain the implantations. Mice treated with 4, 9 and 12mg/(kg body weight day) progesterone along with 28mg/(kg body weight day) dimethoate for days 7 of pregnancy was unable to maintain the implantation with the result there was a 100% pre-implantation loss. There was a significant decrease in the body weight with all the dimethoate and progesterone treated mice. However, uterine weight was significantly decreased with 12mg/(kg body weight day) progesterone along with dimethoate treated mice when compared to controls.

Effect of dimethoate administration schedules on compensatory ovarian hypertrophy, follicular dynamics, and estrous cycle in hemicastrated mice

Dimethoate, a widely used organophosphate insecticide, was administered orally (28 mg/kg body weight) to hemicastrated (HC) virgin mice on day 1 and for 5, 10, and 15 days. Hemicastrated untreated control mice showed a significant increase in relative ovarian weight, with 42.74% hypertrophy and an increase in healthy and atretic follicles when compared with those of sham-operated control animals. The HC mice treated for 1 day or for 5 days showed no significant change in ovarian weight (36.64% and 25.19% hypertrophy, respectively) or in healthy and atretic follicles, when compared with HC-control mice. Treatment with dimethoate for 10 or 15 days, however, resulted in a significant decrease in ovarian weight (19.84% and 0.76% hypertrophy, respectively), a significant decrease in the number of healthy follicles, and a concomitant significant increase in the number of atretic follicles when compared with those in HC control animals. No significant change occurred in the number of estrous cycles or duration of each phase of the estrous cycle in HC mice treated with dimethoate for either 1 or 5 days. In HC mice treated with dimethoate for 10 or 15 days, however, a significant decrease in the number of estrous cycles, duration of proestrus, estrus, and metestrus, a concomitant significant increase in the diestrus phase, when compared with HC control animals. In mice receiving dimethoate for 15 days (but not for 1, 5, or 10 days) a significant decrease occurred in body weight and in the weights of the uterus, kidney, spleen, and liver when compared with the parallel weights in HC control animals. The overall findings suggest that following dimethoate treatment, a significant decrease in ovarian weight with a concomitant increase in compensatory ovarian hypertrophy and in the number of healthy follicles, with a concomitant increase in the number of atretic follicles and interrupted estrous cycles, may be due to the direct effect on the ovary or may be due to a hormonal imbalance in any stage of the hypothalamo-hypophysial ovarian axis.