Cannulation in situ of equine umbilicus. Identification by gas chromatography-mass spectrometry (GC-MS) of differences in steroid content between arterial and venous supplies to and from the placental surface.

The research article discusses a study where the umbilical cords of horses were cannulated in utero (while still in the womb) to analyze the difference in steroid content between arterial and venous supplies, the blood systems that lead to and from the placental surface. The researchers used gas chromatography-mass spectrometry (GC-MS) to identify various steroid components in the plasma samples and explored the role of these steroids in synthesizing estrogen and C18 neutral steroids at the placental surface.

Methodology

• The study involved cannulation of the equine umbilicus, or umbilical cord, while still in utero to procure a series of cord plasma samples for analysis.
• The researchers extracted and derivatised the steroids from these samples. The technique of derivatisation alters the chemical properties of a compound, making it easier to identify using GC-MS.
• GC-MS, a technique combining gas-liquid chromatography and mass spectrometry, was used to analyze and identify the different steroids in the plasma samples.

Findings

• Significant differences were found in the steroid contents of the plasma samples taken from the umbilical artery and vein, the blood vessels that lead to and from the placental surface.
• The analysis identified several major constituents in the arterial plasma samples, mainly as unconjugated steroids. These included 3Beta-hydroxy-5,7-androstadien-17-one, dehydroepiandrosterone, pregnenolone, 3beta-hydroxy-5alpha-pregnan-20-one, 5-pregnene-3beta,20beta-diol, and 5beta-pregnane-3beta,20beta-diol.
• These steroids were also identified in the venous plasma samples but at significantly reduced levels compared to the arterial samples.
• Oestradiol-17alpha, dihydroequilin-17alpha, and dihydroequilenin-17alpha were identified in both arterial and venous plasma samples, mostly as sulphate-conjugated. Higher amounts were detected in plasma sampled from, rather than to, the placental surface.
• No glucuronic acid-conjugated steroids were detected in the study.

Implications

• The findings provide an understanding of the biosynthetic pathways leading to the formation of oestrogens and C18 neutral steroids at the placental surface.
• The distinctions between the steroid contents of the arterial and venous supplies provide new insights into the steroid metabolism in equine placental surface.
• Further studies leveraging these findings could lead to improved healthcare and treatment options for equine reproduction and gestation complications.