Chronic oral exposure to bonny light crude oil (blco) affects estrus cycle, reproductive hormones and organs in female wistar rats

Locals of Nigerian oil producing communities have been known to ingest crude oil via oil spills contaminating their source of drinking water, agricultural produce and marine life that are caught for food. It is also used traditionally as anti-venom, anti-convulsing agent, poison antidote, laxative and analgesic. This exposure has both short term and long term effects, with its long term effects influencing reproduction and reproductive health. This study was carried out to investigate how the chronic exposure to crude oil affects the estrous cycle, hormones and reproductive organs of female Wistar rats. Fifteen nulliparous female rats weighing between 150-200g were randomly divided into three groups. Group 1 (control) received 1ml of distilled water while groups 2 and 3 (test) groups received 100mg/kg body weight and 200mg/kg body weight of Bonny light crude oil (BLCO) respectively via oral gavage for 5 weeks. Vaginal smears of the animals were taken daily and microscopically evaluated for the same period at the end of which the animals were sacrificed. Ovaries and uteri were carefully dissected out, weighed and later sectioned and stained with Hematoxylin & Eosin (H&E) for histopathological analysis. Serum from centrifuged blood was used for gonadotropin and ovarian hormones assay using the Enzyme-linked immunosorbent assay (ELISA) technique. BLCO exposure significantly changed the frequency of some estrous cycle phases in the test group leading to a significant increase in Estrous cycle ratio (ECR), thereby conferring acyclicity on the test groups. There was significant increase in serum estrogen levels and significant reduction in serum progesterone levels as well as significantly reducing progestrone/estradiol (P/E) ratio in the test groups. There were pathological changes in the cellular architecture of ovaries and uteri of the test groups compared to the control. Chronic BLCO exposure affected estrous cycle cyclicity, significantly reduced the P/E ratio and damaged the cellular architecture of reproductive organs of female Wistar rats. BLCO exposure may play a significant role in female infertility.