Induction of ovarian toxicity in the freshwater fish, Pseudetroplus maculatus (Bloch, 1795) after sublethal exposure of dibutyl phthalate

Abstract

Dibutyl phthalate, a plasticizer, is widely used as a softener in several commercial industrial products. The study investigated the sublethal effects of dibutyl phthalate on ovary of the freshwater fish, Pseudetroplus maculatus. Dibutyl phthalate exposed at 0.2 mg/ L concentration for 24, 72 and 96 h showed behavioural modifications in the fish. The body weight showed significant reduction after 72 h of toxicant exposure with concomitant increase in mucous deposition, which indicated whole-organism response against the toxicant. The weight of ovary and gonadosomatic index decreased significantly in all treatment groups thereby suggested the stress exhibited on female reproductive organ. Dibutyl phthalate prevented normal activities of steroidogenic enzymes as 3βand 17β-hydroxysteroid dehydrogenase in ovary of the fish. The alterations in the level of vitellogenin measured through indirect endpoints such as alkali-labile phosphoprotein and total protein in ovary and blood plasma indicated the estrogenic effects of the toxicant. Dibutyl phthalate disrupted hypothalamo-pituitary-gonadal axis as demonstrated by the increase in the levels of luteinizing hormone and testosterone with reduction in serum estradiol without remarkable changes in the level of follicle stimulating hormone. In the ovary, number of vitellogenic oocyte increased whereas the population of pre-vitellogenic oocyte declined without any changes in the number of post-vitellogenic oocyte. Histological evaluation revealed severe morphological damages associated to apoptosis such as empty follicle and atretic oocytes, membrane blebbing, nuclear condensation, vacuolization and broken theca granulosa membrane. The present findings suggested that sublethal exposure of DBP induced ovarian toxicity in the freshwater fish, Pseudetroplus maculatus. Keywords— Dibutyl phthalate, Steroidogenic enzymes, Hormones, Sublethal toxicity, Histology, Pseudetroplus maculatus