Urinary steroids have been studied during early and late pregnancy in
domestic horses or sporadic samples at various stages of pregnancy in wild
equidae. In our studies, urinary estrone sulfate (E1S) and pregnanediol
glucuronide (PdG) were monitored throughout pregnancy in six pony mares by
enzyme immunoassay (EIA). Both hormones were corrected by creatinine (Cr)
index to compensate for the variation in specific gravity. The mean
concentration for ElS, (μg/mg Cr), was .38 ± .03 at d 0, decreased to .17 ±
.04 at d 1, and maintained at less than .5 μg/mg Cr until d 30. Although, there
was an apparent increase to .80 ± .34 at d 34 (NS, P = .122), the first
significant increase was .69 ± .15 at d 46 (P = .0275). Mean concentrations
remained relatively stable at this approximate level until d 60. This level was
followed by a sustained significant increase observed from d 60 onwards.
Mean concentrations of El S increased to 1.11 ± .25, 2.01 ± .45, and 5.48
± 1.47 at d 64, d 76, and d 86, respectively. Levels of EIS further increased
reaching a peak of 143.3 ± 9.51 at d 142 (P = .0006), with maximum for
individual mares ranging from d 114 to 170, and also ranging from 115.4 to
286.1 pg/mg. In all cases, maximum concentrations were followed by a
gradual decline toward parturition with a more rapid decrease 1 to 3 days
before parturition. The first significant decrease following the maximum
concentration was 91.40 ± 13.11 (P = .0024) at d 184. Estrone sulfate was
12.1 ± 3.8 one day prepartum and decreased to .4 ± .1 and .1 ± .01 at d 1
and 4 postpartum, respectively. The mean concentrations of PdG (ng/mg Cr)
increased from 147 ± 4.3 at d 0 to 50.87 ± .17 (NS, P> .05), 36.8 ± 8.1
(P = .016), and 27.6 ± 7.3 (P = .049) at d 6, 8 and 10, respectively. This
increase was followed by a decline and generally the levels fluctuated ranging
from 20 to 30 ng/mg Cr until d 80. At d 86, the PdG levels increased to 54.7
± 11.7 (P = .033). This was followed by a further increase to 141.8 ± 21.4
(P = .0139, compared to d 93) at d 135, then continued to increase to 213.0
± 25.2 at d 198, and remained at this approximate level until d 303. During
the last month of gestation, the mean concentrations of PdG increased from
171.8 ± 9.8 at d 29 prepartum to reach a peak of 388.4 ± 108.6 at d 7
prepartum. Maximum concentrations were followed by a slight decrease to
354.5 ± 84.0 at d 1 prepartum and then decreased to 150.6 ± 23.4 and 39.6
± 9.3 ng/mg Cr at d 1 and 4 postpartum.
In comparing the two hormones, E1S remained baseline followed by a
slight increase at d 35, whereas PdG was relatively stable until both hormones
increased after d 70 of gestation. This might be related to secretion of both
hormones by the fetus and their rapid metabolism by placenta. Estrone sulfate
reached a peak at approximately d 142 followed by a decline toward parturition
while PdG showed a rapid increase from d 70 to 150, followed by a slow
sustained increase to d 300 then increased dramatically again before
parturition, while El S continued to decline. The profile of these urinary
hormones throughout pregnancy appeared to parallel previously published
concentrations in blood. Since the patterns of urinary EIS and PdG are
different, their sites and mechanism of metabolism are likely different. The
results indicate that the presence of the feto-placental unit is important for the
secretion of both estrogens and progestins throughout pregnancy and thus
could be utilized as a reliable method for pregnancy determination after three
months of pregnancy. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36880 |
| Date | 09 February 1993 |
| Creators | Riad, Mohamed Tarek |
| Contributors | Holtan, Donald W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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