Neonatal methyl parathion exposure affects the growth and functions of the male reproductive system in the adult rat

Methyl parathion (MP) is a well-known organophosphorus pesticide, to which humans are exposed in fruit and vegetables as residues of 0-2 mg/kg, children being at higher risk of exposure. The present study was planned to investigate the effects on the adult male reproductive functions of MP following neonatal exposure. New born male Wistar rat pups were treated orally with either 0 or 0.5 mg/kg MP from postnatal day (PND) 3 to PND 28 and sacrificed on PND 98 for the purpose of examination of the reproductive system. Methyl parathion lowered the body weights from days 10 to 24 (p < 0.01), the weights of the reproductive organs (p < 0.05-0.01), the epididymal sperm count (p < 0.01) and the homogenisation-resistant testicular spermatid head count (p < 0.01) and also decreased acid phosphatase (ACP), cholesterol, uric acid, protein, ascorbic acid, and lactate dehydrogenase (p < 0.01) levels in the testis but only ACP and cholesterol in the epididymis. The levels of abnormal sperm and testosterone in the testis were increased (p < 0.01), whereas the leutinising hormone level and total number of seminiferous tubules decreased in the testes of treated rats (p < 0.01). A few tubules showed exfoliation of epithelium and vacuoles. The incidence of stage XIV tubules and ratios of meiotic figures and elongating spermatids to Sertoli cell nucleoli decreased (p < 0.01; Mann-Whitney U test). The present results indicate that MP acts as an endocrine disruptor and consequently affects the postnatal development and growth of the male reproductive organs in the rat. These findings are important to the general public, as there is a chance of children being exposed to this pesticide