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Ovarian disorders in immature rats after postnatal exposure to environmental polycyclic aromatic hydrocarbons
Vladimír Kummer1, Jarmila Mašková, Zdeněk Zralý
1Veterinary Research Institute, Brno, Czech Republic.
Insights
Postnatal exposure to polycyclic aromatic hydrocarbons (PAHs) like benzo(a)pyrene and benz(a)anthracene altered rat ovary development and function. Benzo(k)fluoranthene decreased antral follicles, while benzo(a)pyrene damaged primordial follicles.
Area of Science:
- Reproductive Toxicology
- Environmental Health
- Developmental Biology
Background:
- Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants with potential endocrine-disrupting effects.
- Ovarian development is sensitive to environmental exposures during the early postnatal period.
- Understanding PAH impacts on ovarian morphology and function is crucial for assessing reproductive health risks.
Purpose of the Study:
- To investigate the effects of specific PAHs (benzo(a)pyrene, benz(a)anthracene, benzo(k)fluoranthene) on immature rat ovary development.
- To assess alterations in ovarian histology, follicle counts, apoptosis, theca cell layers, and estrogen receptor beta (ERβ) expression.
- To determine the impact of PAH exposure on ovarian response to ethynylestradiol stimulation.
Main Methods:
- Neonatal rats were exposed daily to benzo(a)pyrene (BaP), benz(a)anthracene (BaA), or benzo(k)fluoranthene (BkF) from postnatal day 1 to 14.
- Doses ranged from 0.1 to 10.0 mg kg(-1), with ethynylestradiol (EE) and vehicle controls used for comparison.
- Ovarian morphology, follicle dynamics, apoptosis, ERβ expression, and EE response were evaluated on day 23.
Main Results:
- BaP and BaA exposure increased antral and non-atretic follicles, granulosa cell apoptosis, and theca cell layer thickness.
- BkF exposure decreased antral follicles but did not affect other parameters.
- BaP exposure led to primordial oocyte degeneration, impairing a significant percentage of primordial follicles, and altered ovarian ERβ expression.
Conclusions:
- Postnatal exposure to BaP, BaA, and BkF significantly alters ovarian morphology and ERβ expression in immature rats.
- These PAHs can induce ovarian dysfunction, including impaired follicle development and oocyte damage.
- The findings highlight the potential reproductive risks associated with early-life exposure to environmental PAHs.
Abstract:
The study investigated the effects of postnatal exposure to polycyclic aromatic hydrocarbons (PAHs) on the development of the rat ovary. Neonates were injected on each postnatal day 1-14 with benzo(a)pyrene (BaP), benz(a)anthracene (BaA) and benzo(k)fluoranthene (BkF) (0.1, 1.0, 5.0 or 10.0 mg kg(-1)), ethynylestradiol (EE; 1.0 µg kg(-1)) or a vehicle (control group). The rats were killed on day 23. Postnatal exposure to BaP increased the total number of antral follicles in ovaries (P < 0.05) and the number of nonatretic follicles (P < 0.01) as a result of a lower degree of apoptosis of granulosa cells, and the thickness of theca cell layers (P < 0.01). Similar histological findings were observed after BaA administration. Conversely, BkF exposure caused a decrease in the number of antral follicles, but did not alter the other investigated parameters. Degeneration of primordial oocytes after exposure to PAHs was observed only after exposure to BaP. Treatment with BaP at doses of 1.0 and 10.0 mg kg(-1) impaired 28.1 and 60.3% of the primordial follicles, respectively. Substantial alterations in ovarian ERβ expression were detected in the rats; their intensity differed with the type of PAH. Response of the ovaries to EE (three injections of 1.0 µg kg(-1) on postnatal days 20-22) in rats exposed to PAHs was suppressed in contrast to the controls. The study showed that postnatal exposure to BaP, BaA and BkF altered ovarian ERβ expression, disturbed morphological development of the ovaries and caused ovarian dysfunction in immature rats.
