Placental angiogenic and hormonal factors are affected by thyroid hormones in rats

The objective of the present study was to evaluate the effect of the thyroid hormones in the gene transcription and immunohistochemical expression of hormonal and angiogenic factors in the placenta of rats. Seventy-two adult female rats were divided equally into propylthiouracil (PTU)-treated, thyroxine (T4)-treated, and control groups. The animals were sacrificed at 10, 14, and 19 days of gestation. We evaluated the immunohistochemical expression of VEGF and its receptor Flk-1. The gene transcription of VEGF, Flk-1, PGF, sFlt1, PL-1, and rPlf was evaluated in placental discs by real-time RT-PCR. The data were analyzed using a Student-Newman-Keuls (SNK) test. At day 10, T4-treated rats presented increased VEGF and PGF gene expression, while PTU-treated rats showed increased rPlf gene expression. Both groups showed reduced Flk-1 and PL-1 gene expression at day 10. At day 14, PTU-treated rats showed reduced VEGF, PGF, and rPlf gene expression. PTU-treated group showed reduced VEGF immunostaining in the placental labyrinth at 14 and 19 days of gestation but it showed increased VEGF immunostaining in the spongiotrophoblast layer at day 14. PTU-treated rats showed increased Flk-1 expression at 14 days of gestation. At days 14 and 19, T4-treated group showed increased PL-1 gene expression and reduced VEGF immunostaining. T4-treated rats also showed reduced Flk-1 and sFlt-1 expression at day 19. Both groups showed increased rPlf gene expression at day 19. In conclusion, rats treated with PTU and T4 have differential effects on the expression of factors involved in placental angiogenic and hormonal activity, and these effects are dependent on the gestational period.