Changes in urinary and plasma oestrone sulphate concentrations after induction of foetal death in mares at 45 days of gestation

Abstract

Foetal death was induced in 10 Standardbred mares at day 45 of gestation by injecting 20 to 45 ml of hypertonic (24% W/V) saline into the conceptus at surgery. Ten mares underwent sham treatment and acted as controls. Blood and urine samples were collected every other day between days 30 and 45 post ovulation and at 0, 3 and 6 h relative to the infusion of saline in the treated mares, or sham treatment in control mares. Blood and urine samples were then collected daily between days 46 and 55 post ovulation. Urine oestrone sulphate (E1S) concentrations, measured by radioimmunoassay, increased between day 34 and day 36 of gestation in treated and control groups. In mares in which foetal death was induced, urine E1S concentrations declined post-operatively and were significantly (p less than .05) lower than controls by day 50. In plasma, E1S concentrations showed a major increase between days 36 and 40 in both groups. This was followed by a rapid decline after treatment in saline-injected mares, so that by day 48 plasma E1S concentrations in treated mares were significantly (P less than .05) lower than the controls. The results show that urinary and plasma E1S concentrations rise rapidly during early pregnancy, and are associated with a viable foetus after day 45 of pregnancy.

Concentrations of sulphated estrone, estradiol and dehydroepiandrosterone measured by mass spectrometry in pregnant mares

“…The fetal gonads express high levels of the enzymes required for androgen synthesis based on transcript analysis [28], and has high tissue concentrations of DHEA [28,29] that are secreted into the fetal circulation [28,30]. Most convincingly, fetal gonadectomy resulted in an immediate decline in maternal oestrogen concentrations [31][32][33], as does death of the equine fetus [13,34] Equine embryos collected from day 12 to 15 express aromatase [35] and embryos from 12 to 20 days post fertilisation were shown to accumulate upwards of 3 lg/mL of estrone sulphate in yolk-sac fluid [36]. Thereafter however, the equine placenta has little ability to synthesise its own androgen substrate [28,37] but, like the equine embryo, has considerable capacity to synthesise oestrogen if provided with androgen substrate [37][38][39].…”

Absence of Effects From Immunocontraception on Seasonal Birth Patterns and Foal Survival Among Barrier Island Wild Horses

“…Both metabolites are significantly higher in pregnant animals. However, although progesterone levels (and therefore iPdG) will remain high for months after a fetal death, E1C concentrations fall within 12 hr of fetal loss (Hyland & Langsford, 1990). Thus, the pregnancy detection methods are virtually 100% accurate.…”

Review of the reproductive endocrinology of the pregnant and parturient mare

“…Additional confirmation of an increase in testosterone during equine pregnancy by mass spectrometry would be welcome [196]. Fetal androgen synthesis ceases when the fetus dies and is associated with a rapid decline in estrogen concentrations [127,128]. These changes in steroid profiles occur within days of fetal demise, so that constant monitoring (multiple times per week) would likely be necessary to predict impending abortions.…”