Delayed adverse effects of neonatal exposure to polymeric nanoparticle poly(ethylene glycol)-block-polylactide methyl ether on hypothalamic–pituitary–ovarian axis development and function in Wistar rats

• Neonatal exposure to polymeric nanoparticle PEG-b-PLA in female Wistar rats.
• Delayed effects on hypothalamic–pituitary–ovarian axis development and function were studied.
• Acceleration of the puberty onset and irregular cyclicity were observed.
• Pituitary hyperemia, vascular dilatation and congestion, altered pituitary LH release and increased progesterone serum levels were detected.
• Possible neuroendocrine disrupting effect of PEG-b-PLA nanoparticles is proposed.

We studied delayed effects of neonatal exposure to polymeric nanoparticle poly(ethylene glycol)-block-polylactide methyl ether (PEG-b-PLA) on the endpoints related to pubertal development and reproductive function in female Wistar rats from postnatal day 4 (PND4) to PND 176. Female pups were injected intraperitoneally, daily, from PND4 to PND7 with PEG-b-PLA (20 or 40 mg/kg b.w.). Both doses of PEG-b-PLA accelerated the onset of vaginal opening compared with the control group. In the low-dose PEG-b-PLA-treated group, a significantly reduced number of regular estrous cycles, increased pituitary weight due to hyperemia, vascular dilatation and congestion, altered course of hypothalamic gonadotropin-releasing hormone-stimulated luteinizing hormone secretion, and increased progesterone serum levels were observed. The obtained data indicate that neonatal exposure to PEG-b-PLA might affect the development and function of hypothalamic–pituitary–ovarian axis (HPO), and thereby alter functions of the reproductive system in adult female rats. Our study indicates a possible neuroendocrine disrupting effect of PEG-b-PLA nanoparticles.