Changes in maternal pregnane concentrations in mares with experimentally-induced, ascending placentitis.

The study investigates the changes in concentrations of various pregnane compounds in the blood plasma of pregnant mares who have been experimentally induced with ascending placentitis. Through sophisticated chromatographic techniques, the researchers identify significant changes specific to the condition that could improve future diagnosis and understanding of the disease in horses.

Introduction to the Research

• This research is centered around understanding the changes in the concentrations of several pregnanes (progesterone and other related hormones) in mares with experimentally-induced, ascending placentitis.
• Ascending placentitis is a type of infection that moves up from the lower regions of the body and affects the placenta, and it was induced here using the bacteria Streptococcus equi spp. zooepidemicus.
• Comparison was made to a control group of healthy pregnant mares at the same stage of pregnancy.
• Two groups of mares with induced placentitis were studied: those that ended in premature births within eight days (acute) and those that gave birth after eight or more days (chronic).

Methodology

• Advanced analytical methods were used to measure the concentrations of various pregnanes in the blood plasma of the mares for a set period before the act of abortion.
• The concentrations of progesterone (P4), 5α-dihydroprogesterone (DHP), allopregnanolone, 3β-hydroxy-5α-pregnan-20-one (3β5P), 20α-hydroxy-5α-pregnan-3-one (20α5P), 5α-pregnan-3β,20α-diol (βα-diol), and 5α-pregnan-3β,20β-diol (ββ-diol) were measured.
• These measurements were performed using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) and Immunoassay for immunoreactive P4.

Findings

• In mares with chronic placentitis, concentrations of DHP and its downstream metabolites surged 2-8 days prior to abortion compared to control mares.
• Particularly, 20α5P and βα-diol showed the highest increase (approximately 3 to 4 times) 8 days before abortion in mares with chronic placentitis compared to control mares.
• In the case of mares with acute placentitis, concentrations of DHP, allopregnanolone, 3β5P, 20α5P, and βα-diol were observed to decrease within 0-3 days prior to abortion.
• Progesterone concentrations did not show major fluctuations in mares with chronic placentitis and was detected at low concentrations in control mares’ samples.
• However, in mares with chronic placentitis, Immunoreactive-P4 heightened two days before abortion.

Conclusions

• The patterns of increased placental metabolized pregnanes in mares with chronic placentitis resembled the changes in maternal pregnanes found in normal mares at later stages of gestation, suggesting that these patterns could reflect fetal stress and adrenal activity affecting pregnane metabolism.
• The decrease in these pregnanes in acute cases likely indicates severe fetal or placental compromise.
• These findings provide a stepping stone towards a more comprehensive understanding of the patho-physiological changes in mares affected by ascending placentitis and could guide the development of more effective diagnostic tools for this condition in horses.