INITIATION OF PARTURITION IN THE GOAT: EVIDENCE FOR CONTROL BY FOETAL GLUCOCORTICOID THROUGH ACTIVATION OF PLACENTAL C21-Steroid 17α-Hydroxylase

Flint, A. P. F.; Kingston, Elizabeth; Robinson, J. S.; Thorburn, G. D.

doi:10.1677/joe.0.0780367

Cited by 75 publications

(33 citation statements)

References 19 publications

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“…2) is less certain. One possibility is that it results from the activation or induction of placental enzymes which metabolize C21 steroids to oestrogens; an increase in placental 17a-hydroxylase activity in response to raised fetal glucocorticoid concentrations has been implicated in the mechanisms leading to the onset of labour in goats (Flint et al, 1978), and a similar series of events is thought to occur, and to cause a decrease in placental progesterone secretion, in sheep before parturition (see Flint & Ricketts, 1979).…”

Section: Discussionmentioning

confidence: 99%

“…However, the uptake of progesterone by the gravid uterus decreases after approximately 110 days gestation (Thorburn & Schneider, 1972), and the placenta contains 3 ß-hydroxysteroid dehydrogenase after Day 116 (Wiener, 1976;Flint, Kingston, Robinson & Thorburn, 1978). Therefore it seems possible that the placenta may produce small amounts of progesterone during late pregnancy.…”

Section: Introductionmentioning

confidence: 99%

“…Concentrations of progesterone and total unconjugated oestrogens (oestradiol-17ß plus oestradiol-17a plus oestrone) were measured in plasma by radioimmunoassay s described elsewhere (Flint, Anderson, Patten & Turnbull, 1974;Sheldrick, Mitchell & Flint, 1980). These assays have previously been validated for plasma from goats (Flint et al, 1978); for the progesterone and oestrogen assays the respective values were 84 and 91% for mean extraction recovery, 8-5 and 8-6% for intra-assay coefficient of variation, and 5-4 and 4-0% for the inter-assay coefficient of variation. The sensitivities were 0-016 ng progesterone/ml and 5-6 pg total oestrogens/ml.…”

Section: Introductionmentioning

confidence: 99%

“…1). An important metabolite of progesterone in vitro, which is known to circulate at high concentrations in late gestation, is 5ß-pregnane-3a,20a-diol (Flint et al, 1978 overnight at 4°C. To separate free and bound steroid, 0-5 ml of a solution of polyethylene glycol-6000 (30% w/v in water) was added, and after vortex mixing for 1 min, -globulins were sedimented by centrifugation (1000 g for 30 min).…”

Section: Introductionmentioning

confidence: 99%

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Placental production of progesterone in ovariectomized goats treated with a synthetic progestagen to maintain pregnancy

Sheldrick¹,

Ricketts²,

Flint³

1980

Reproduction

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Placental production of progesterone in ovariectomized goats treated with a synthetic progestagen to maintain pregnancy

Sheldrick¹,

Ricketts²,

Flint³

1980

Reproduction

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“…The relations between mammary function and the major hormonal F. M. MA ULE WVA LKER AND M. PEA KER changes occurring in late pregnancy and at parturition have recently been described in the goat and a hypothesis proposed (Davis, Fleet, Goode, Hamon, Maule Walker & Peaker, 1979) to link these events with the initiation of parturition in this species (Flint, Kingston, Robinson & Thorburn, 1978).…”

Section: Introductionmentioning

confidence: 99%

Local production of prostaglandins in relation to mammary function at the onset of lactation in the goat.

Walker¹,

Peaker²

1980

The Journal of Physiology

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SUMMARY1. Arterial and mammary venous concentrations of prostaglandins F. (PGFa), E (PGE) and the PGFa metabolite, 13,14-dihydro-15-oxoPGFa (DHK-PGFe) were studied during late pregnancy and the onset of lactation in conscious goats. Mammary secretion concentrations of PGFa and DHK-PGFa were determined, and mammary blood flow, arterial plasma progesterone concentrations and milk composition were also studied.2. A significant output of PGFa from the mammary gland into mammary venous blood was observed during late pregnancy; this output ceased near term.3. Mammary output of DHK-PGFa into venous blood began about 6 days prepartum, suggesting an increasing capacity of the gland to metabolize PGFa.4. The concentration of PGFa in mammary secretion increased from about 4 days pre-partum, that of DHK-PGFa from about 12 days pre-partum.5. It is concluded that although total mammary output of PGFa decreases during late pregnancy and early lactation, the rate of mammary synthesis of PGFa increases and the PGFa is increasingly secreted into milk and metabolized to DHK-PGFe within the mammary gland.

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Pregnancy determination in the Asian elephant (Elephas maximus): A change in the plasma progesterone to 17α hydroxyprogesterone ratio

1997

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The measurement of circulating progesterone (P) is widely used to confirm and monitor pregnancy in the captive Asian elephant. Consistently elevated progesterone (P) concentrations for a minimum of 12 weeks can be used as a positive indication of pregnancy, although two instances of prolonged P secretion during the cycle have been recorded [Rübel, 1987; Olsen et al., 1994]. Previously, we demonstrated that pregnanetriol was the major urinary gestagen metabolite enabling the noninvasive monitoring of the reproductive cycle of the Asian elephant [Niemuller et al., 1993] as well as pregnancy [unpublished data]. The importance of this unusual urinary metabolite triggered an investigation into the secretion of circulating concentrations of 17α hydroxyprogesterone (17α OHP) during pregnancy and reproductive cycles, as this steroid is the only steroid precursor of pregnanetriol. Comparison of the profiles between 17α OHP and P during early pregnancy (n = 5) and nonconceptive cycles (n = 15) demonstrated a decline in 17α OHP, but not P, as early as week 3 postmating (designated as week 1) and lasting up to week 13. Otherwise, secretions of 17α OHP mimicked P concentrations throughout pregnancy and in nonconceptive cycles. Examination of the mean ratio values of 17α OHP to P demonstrated a significant drop in the ratio during weeks 2–7 of early pregnancy from ≥0.7 to <0.7 compared with the same time period in a nonconceptive cycle (P < 0.05, N = 5). A 2×2 table analysis of the 17α OHP:P ratio during weeks 2–7 indicated that the possibility of a false positive or false negative result was 3.4 and 6.5%, respectively, based on the sensitivity and specificity of the test. Overall, gestation lengths of the pregnancies completed during this study (N = 4) ranged from 91 to 98 weeks, with a mean of 93.6 ± 2.9 (SEM) weeks. A birth‐to‐conception interval of 47 weeks was noted in one animal. The results described in this report provide additional data on the reproductive endocrinology of the pregnant Asian elephant and also present the earliest means to date of determining pregnancy by analysis of the 17α OHP:P ratio. Zoo Biol 16:415–426, 1997. © 1997 Wiley‐Liss, Inc.

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INITIATION OF PARTURITION IN THE GOAT: EVIDENCE FOR CONTROL BY FOETAL GLUCOCORTICOID THROUGH ACTIVATION OF PLACENTAL C21-Steroid 17α-Hydroxylase

Cited by 75 publications

References 19 publications

Placental production of progesterone in ovariectomized goats treated with a synthetic progestagen to maintain pregnancy

Placental production of progesterone in ovariectomized goats treated with a synthetic progestagen to maintain pregnancy

Local production of prostaglandins in relation to mammary function at the onset of lactation in the goat.

Pregnancy determination in the Asian elephant (Elephas maximus): A change in the plasma progesterone to 17α hydroxyprogesterone ratio

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