Effect of Monocrotophos on Pubertal Development, Reproductive and Thyroid Axis in Male Wistar Rats

The male pubertal assay is a Tier I screening assay to detect potential endocrine active chemicals (EAC) acting through a variety of steroid hormone and thyroid hormone receptor-mediated and non-receptor-mediated mechanisms. This study reports the effect of monocrotophos technical (MCT) on pubertal development and thyroid function in the intact juvenile/peripubertal male rats. Water (RO) was administered in Group 1 animals (negative control group). 1-Chloro-2-nitrobenzene (CNB) was administered to Group 2 (positive control group) animals at 100 mg kg⁻¹. MCT was administered to Group 3, Group 4, and Group 5 animals at 0.1, 1.0 and 2.0 mg kg⁻¹, respectively. On post netal day 53, blood was collected for clinical pathology and hormone analysis. After sacrifice through decapitation, necropsy was performed and organs were collected. Shivering was observed for 3–4 h in all the rats treated with MCT at 1.0 and 2.0 mg kg⁻¹. Significant reduction in body weight, body weight gain and feed consumption was observed in the rats treated with CNB and MCT (2.0 mg kg⁻¹). Body weight at complete preputial separation was significantly decreased in rats treated with MCT (2.0 mg kg⁻¹). Significant increase in alanine amino transferase (ALT), phosphorus, blood urea nitrogen (BUN), and urea was observed in the animals treated with MCT at 2.0 mg kg⁻¹. Significant decrease in serum testosterone was observed in the animals treated with MCT (2.0 mg kg⁻¹). Reduction in body weight or serum testosterone level and marginal delay in puberty in MCT (2.0 mg kg⁻¹) treated group could be due to systemic toxicity. It was concluded that MCT is not a thyroid toxicant based on serum thyroid hormone level and microscopic examination.