243 IMPACT OF MATERNAL LOW-DOSE ESTRADIOL-17β EXPOSURE DURING PREGNANCY ON THE REPRODUCTIVE ORGANS OF MALE PIG PROGENY

In male developing piglets, low endogenous oestrogenic hormone levels prevail. Sensitive tissues expressing high levels of oestrogen receptors, such as the epididymis, might thus be of specific relevance for early disturbances by estrogenic endocrine disruptors. We have previously shown that distinct concentrations of the natural oestrogen oestradiol-17β (E2) orally applied during the whole period of pregnancy in sows lead to a distinct shift in body composition. Therefore, we aimed at investigating whether prenatal E2 exposure had the potential to program male reproductive organs toward altered semen quality. The E2 treatment groups (n = 4 sows/group) were designed to represent doses of pharmacological relevance (PR; 1000 µg kg–1 of body weight per day), oral no-effect level (10 µg kg–1 of body weight per day), and acceptable daily intake level (0.05 µg kg–1 of body weight per day). Total RNA was extracted from the epididymis of 8-week-old piglet twins (n = 2 per sow). The RNA of littermates was pooled and subjected to microarray analysis (MA) using Agilent Porcine Genome Arrays (Agilent Technologies Inc., Santa Clara, CA, USA). Ejaculates of adult male pigs from the control group and the pharmacological group (n = 4) were collected and analysed for quantitative and qualitative parameters by using computer-assisted sperm analysis and flow cytometry. In total, 105 transcripts exhibited a significant difference of more than 1.5-fold for at least one of the treatment groups compared with the control group (P < 0.05; FDR 5%). Several transcripts revealed gradually decreasing amounts subject to the dose of E2 exposure. Eight transcripts showed significant differences in all 3 treatment groups compared with the control group. Thirty-two transcripts had reduced abundance in the PR group and the oral no-effect level group, whereas 20 transcripts were downregulated in the PR group only. Semen parameters of adult males did not differ regarding volume and semen concentration, morphology, and membrane integrity. Computer-assisted sperm analysis evaluations did not show differences in motility and other kinematic parameters. Eight weeks after E2 exposure, male prepubertal piglets exhibited significant differences in epididymal messenger RNA transcript abundance subject to an in utero E2 treatment. This points toward possible epigenetic programming of the epididymis. Although the differential transcript abundance indicates a perturbation, normal semen quality was found after adolescence. Either these transcriptional changes are of minor functional importance or flexible mechanisms account for the developmental adaptations. Considering that identical transcripts were regulated in offspring exposed to both pharmacological and very low doses, further investigations of set points obviating long-term adverse consequences are needed.