A broad-spectrum organophosphate pesticide O,O-dimethyl O-4-nitrophenyl phosphorothioate (methyl parathion) adversely affects the structure and function of male accessory reproductive organs in the rat.

Methyl parathion (MP) is an organophosphate pesticide used in agriculture, but also illegally used to spray homes and businesses to control insects. The present study was designed to investigate adverse effects of MP on accessory reproductive organs. Male Wistar rats aged 13-14 weeks were treated and sacrificed as follows. Experiment 1: 0.0 (water vehicle), 1.75, 3.5 or 7mg/kg (i.p.) for 5 days and sacrificed on day 14; experiment 2: 0.0, 0.5 or 1mg/kg (i.p.) for 12 days and sacrificed on day 130; experiment 3: 0.0, 0.5 or 1mg/kg (i.p.) for 12 days and sacrificed on day 77; experiment 4: 0.0, 0.75 or 1.5mg/kg (i.p.) for 25 days and sacrificed on day 17 and experiment 5: 0.0 or 3.5mg/kg (p.o.) for 25 days and sacrificed on day 17, after the last exposure. The accessory reproductive organs were removed, weighed and processed for histopathological analysis. Structural qualitative changes such as epithelial cell morphology and luminal observations were carried out for each organ in all experiments. Epididymis of one side was homogenized and biochemical estimations of acid phosphatase (ACP), cholesterol, total protein, uric acid, and Vitamin C were conducted by calorimetric methods in experiments 4 and 5. In experiment 1 the organ weights did not change; in experiment 2, the epididymal weight increased (P<0.001); in experiment 3, the weights of ductus deferens decreased at 1mg/kg and that of seminal vesicle decreased at both dose-levels (P<0.001). In experiments 4 and 5, weights of epididymis and prostate decreased, whereas in experiment 5, weights of ductus deferens and seminal vesicle increased (P<0.05-0.001). The sperm density was normal in control, moderately decreased in experiment 1 at 3.5 and 7mg/kg; in experiment 2 at 1mg/kg, and in experiment 5 at 3.5mg/kg, and severely decreased in experiment 3 at 1mg/kg and in experiment 4 at both dose-levels. The epithelial necrosis and nuclear pyknosis were seen in experiments 1, 3, 4 and 5, whereas nuclear degeneration was seen in experiment 1 and 4 and germ cells in the lumina of epididymis were seen in experiment 4. The nuclear pyknosis in the ductus deferens was seen in all experiments, except at 1.75mg/kg in experiment 1 and at 0.5mg/kg in experiment 3. Brush border disruption in the ductus deferens was seen in experiments 1 and 4; sperms were seen in the lumen in experiment 1 at 7mg/kg, and in experiments 4 and 5. The vacuoles in the epithelium were seen in experiments 1 and 4 and immature germ cells were seen in the lumen in experiment 4. The ACP and Vitamin C levels decreased in experiment 4 at both dose-levels, and in experiment 5 all biochemical parameters tested found decreased (P<0.01-0.001). The present results indicate that MP affects the structure and function of accessory reproductive organs in the rat.