Effect of a povidone-iodine intrauterine infusion on progesterone levels and endometrial steroid receptor expression in mares

Abstract

Background: Intrauterine infusions have been widely used for the treatment of endometritis in the mare. Nevertheless, their consequences on endocrine and endometrial molecular aspects are unknown. We studied the effect of a 1% povidone-iodine solution intrauterine infusion on progesterone levels, endometrial histology and estrogen (ERα) and progesterone (PR) receptor distribution by immunohistochemistry.

Methods: Fourteen healthy mares were used in this study. Estruses were synchronized and seven mares were treated with intrauterine infusions at days 0 and 2 post ovulation of two consecutive estrous cycles. Uterine biopsy samples were taken on days 6 and 15 post ovulation.

Results: The treatment did not induce an inflammatory response indicating endometritis, neither affected the ERα. However, it reduced the percentage of PR positive cells (PPC) on day 6 (deep glandular epithelium, control: 95.7 vs. infused: 61.5, P < 0.05). Treated mares tended to have lower progesterone levels on day 2 (3.9 ng/ml vs. 6.6 ng/ml, P = 0.07), and higher levels on day 15 compared with controls (4.4 ng/ml vs. 1.3 ng/ml, P = 0.07).

Conclusion: a 1% povidone-iodine infusion during days 0 and 2 post ovulation in healthy mares did not induce histological changes indicating endometritis, but altered progesterone concentrations and reduced the expression of endometrial PR at day 6 without affecting the ERα. These changes could reduce embryo survival.

Figure 1

Mean (± s.e.m) progesterone concentrations of control (open squares) and infused (solid triangles) mares. Samples of consecutive cycles were pooled. Arrows indicate days of treatment of the infused group.

Figure 2

Immunohistochemical localisation of estrogen receptor α in representative endometrial cross sections of mares on days 6 and 15 in the control group (a; c) and the infused group (b; d), respectively. (e = negative). Original magnification × 100 and × 400. Scale bars = 100 μm. Gs, superficial glandular epithelium; Gd, deep glandular epithelium; LE, luminal epithelium; ST, stroma.

Figure 3

Immunohistochemical localisation of progesterone receptor in representative endometrial cross sections of mares on day 6 and 15 in the control group (a; c) and the infused group (b; d), respectively. Original magnification × 100 and × 400. Scale bars = 100 μm.

Figure 4

Percentage of positive cells of estrogen receptor α (ERα; left panel) and progesterone receptor (PR; right panel) in control and infused mares on days 6 (open bars) and 15 (solid bars) post ovulation. Bars with different superscripts within the same graph differ: a, b P <0.05.