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.
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