Graduate Thesis Or Dissertation
 

Plasma and fecal progestins during placentation in the mare

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  • Aims of this research were to find the time period and specific progestins reflective of the transition from ovarian source to placental source during early gestation in mares. An attempt was made to describe an accurate profile of total and individual progestins in plasma and feces from 64 to 150 days of gestation. There was also an attempt to determine if plasma and fecal progestins increased around 90 days of gestation as previously reported in this laboratory for urinary hormones, estrone sulfate (E1S) and pregnanediol glucuronide (PdG). Blood and fecal samples were collected and ovaries were examined via ultrasound every other day from days 64 to 150 of gestation. Plasma and fecal samples were analyzed using gas chromatography/mass spectrometry (GC/MS) with steroid derivatization. Eight progestins in plasma and ten progestins in feces were identified and quantified. In plasma, 20α-hydroxy-5α-pregnan-3-one (20α-5α) was found in highest concentration, while 5α-pregnane-3β,20β-diol (ββ-diol) was highest in feces. Progestins averaged approximately 100 times higher in feces than in plasma, while ββ-diol was about 800 times higher. There was a linear, parallel increase over time (P<0.05, ANOVA) for total progestins. There was a high, positive correlation between plasma and feces for most progestins, the exception being progesterone (P4), which was negatively correlated because over time, concentrations in plasma decreased while increasing in feces. Log ratios of feces to plasma indicated some progestins increased faster in plasma than feces, and vice-versa, while some remained constant. Spline regression (Gauss-Newton, SAS) analysis of the four main progestins, 3β-hydroxy-5apregnan- 3-one (3β-5α), 20α-5α, 5α-pregnane-3β,20α-diol (βα-diol), and ββ-diol, indicated a difference in the rate of increase over time, occurring at about 112.7 days of gestation in plasma and 109 days of pregnancy in feces, which was nearly 20 days later than that reported for urine. Although the time of change in the rate of increase was highly variable among mares and specific progestins, for most, a clear change was evident by 115 days of gestation. This likely represents a functional feto-placental unit, fully capable of pregnancy maintenance.
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