An investigation on imidacloprid induced reproductive toxicity in pregnant rats
Abstract
Imidacloprid, a neonicotinoid insecticide is widely and most commonly used insecticide in soil, seed and
foliar application for the control of sucking insects and some beetles and as an ectoparasiticide in veterinary
medicine. There is very little data available on reproductive toxicity in female mammalian system. The study was
planned to investigate the imidacloprid induced reproductive toxicity in pregnant rats. The study was comprised of
two experiments and imidacloprid was administered in both experiments at two dose levels (19 and 38 mg/kg/day)
which is equal to 1/20th and 1/10th of LD50, respectively, in female rats. Control animals were administered 3%
gum acacia solution at the dose of 1 ml/100g b. wt. Each group comprised of 12 female rats and six male rats. One
male rat was used to mate with two female rats. Male rats of second experiment were treated with imidacloprid.
In first experiment, untreated male rats were used for mating with untreated female rats and female rats
were then treated with IMI from day 6 to 19 of gestation. In second experiment, male rats were treated for one
spermatogenic cycle (70 days) and upto the day of mating while female rats were treated for two oestrus cycle (14
days) prior to mating, during mating and upto day 19 of pregnancy. Female rats were killed on the day 20 of
gestation in both experiments.
Different parameters undertaken in female rats of both experiments were body weight, necropsy
findings, relative weight of vital organs, morphometric measurements (adrenal gland, ovary, placenta and foetus),
tissue biochemicals (MDA, GSH, cholesterol and total protein), blood/plasma biochemicals (albumin, BUN,
cholesterol, creatinine, glucose, GSH, MDA, triglyceride, total plasma protein) level, plasma enzymes (AST, ALT,
ALP) level, progesterone level and parameters of gravid uterus (Weight of gravid uterus, no. of foetus in both
uterine horns, no. of implantation sites in both uterine horns, foetal malformation and gross changes in placenta
and weight of foetal heart, liver and kidneys).
Imidacloprid did not produce significant changes in body weight, relative organ weight, and
morphometric measurements of adrenal gland, ovary, foetus and placenta, relative weight of gravid uterus, average
no. of foetus, average no. of implantation sites, average foetal and placental weigh and relative foetal organ weight.
Imidacloprid produced a non-significant increasing trend of plasma cholesterol level, plasma triglyceride
level and plasma glucose level at 19 and 38 mg/kg dose in both experiments. A significant increase in MDA level
in both experiments in adrenal gland and ovary at 38 mg/kg dose and in plasma at 19 and 38 mg/kg dose was
observed. A significant decrease in GSH and total protein levels of adrenal gland and ovary was produced at 19
and 38 mg/kg dose in both experiments. A non-significant decrease in cholesterol level of adrenal gland and ovary
was produced at 19 and 38 mg/kg in both experiments. A significant decrease in total protein and albumin level of
plasma was produced at 38 mg/kg dose in both experiments. A significant increase in creatinine level of plasma
was produced at 38 mg/kg dose in first experiment and at 19 and 38 mg/kg dose in second experiment. A
significant increase in BUN level of plasma was produced at 38 mg/kg dose level in second experiment. A
significant increase in ALT level in plasma was produced at 38 mg/kg dose in first experiment and at 19 and 38
mg/kg dose in second experiment. A significant increase in AST level in plasma was produced at 19 and 38 mg/kg
dose in both experiments. A significant increase in ALP level in plasma was produced at 38 mg/kg dose in second
experiment. A significant decrease in progesterone level of plasma was produced at 38 mg/kg dose in second
experiment.
16.66% of female rats of 38 mg/kg dose group of second experiment were not conceived after mating
with fertile adult male rats. 30% female rats of 38 mg/kg dose group and 8.33% female rats of 19 mg/kg dose
group of second experiment showed foetal malformations and gross placental changes. Malformed foetuses were
necrotic, deep red colored (dead), congested and resorpted. Gross placental changes produced were white spots,
area of necrosis and yellowish discolouration and thickening of placenta. No foetal alterations and gross placental
changes were observed in first experiment.