Habibollah Johari - Department of Biology, Islamic Azad University, Darab Branch, Darab, Iran.
Mehrdad Shariati - Department of Biology, Islamic Azad University, Kazeron Branch, Kazeron, Iran.
Shahram Abbasi - Department of Biology, Islamic Azad University, Kazeron Branch, Kazeron, Iran.
Esfandyar Sharifi - Department of Biology, Islamic Azad University, Kazeron Branch, Kazeron, Iran.

Background: Diazinon is a widely used Organophosphate insecticide, which is applied against plant pests. This compound has various side effects because it acts as an acetyl cholinesterase enzyme inhibitor.Objective: The aim of present study was to investigate the effects of diazinon on pituitary–gonad axis and ovarian histological changes in rats.Materials and Methods: In total, 50 female wistar rats were divided into 5 groups of 10, including control, sham and experimental groups I, II and III which orally received 50, 100 and 150 mg/kg/bw diazinon for 14 days respectively. Diazinon was administered orally, and 24 hours after the last treatment, blood samples were taken from the heart, centrifuged and sera were evaluated for the concentrations of estrogen, progesterone and gonadotropins via RIA method. In addition, ovaries were removed, fixed and studied with steriological methods.Results: The results show no significant changes in body weight among various groups; while, ovarian weight in experimental group III decreased significantly (p<0.05). Also, no significant changes in the levels of LH, FSH and estradiol hormones were observed. In contrast, the concentration of progesterone showed a significant decrease in all experimental groups compared with the control group. The results showed no significance difference in the mean number of primary, secondary and graffian follicles but there was a significant decline in the mean number of corpus luteum in experimental group receiving 150 mg/kg diazinon (p<0.05 ) .Conclusion: One can conclude that oral administration of diazinon could have adverse effect on progesterone hormone level as well as hazardous effects on ovarian tissues and reproductive processes.

Diazinon, Progesterone, Estrogen, Ovary, Rat