EFFECT OF PROGESTERONE WITHDRAWAL IN SHEEP DURING LATE PREGNANCY

1982 ◽  
Vol 92 (1) ◽  
pp. 85-93 ◽  
Author(s):  
M. J. TAYLOR ◽  
R. WEBB ◽  
M. D. MITCHELL ◽  
J. S. ROBINSON
Keyword(s):  
Dehydrogenase Activity ◽  
Plasma Concentrations ◽  
Late Pregnancy ◽  
Hydroxysteroid Dehydrogenase ◽  
Peripheral Plasma ◽  
Activity Concentrations ◽  
Pregnant Sheep ◽  
Prostaglandin F

The concentration of progesterone in the peripheral plasma of seven sheep during late pregnancy was reduced by injection of an inhibitor of 3β-hydroxysteroid dehydrogenase activity. Concentrations of progesterone were 10·0± 1·0(s.e.m.) ng/ml (n = 6) before injection of the inhibitor, fell to 1·39 ± 0·40 ng/ml (n = 6) 30 min after injection, and remained within this lowered range for 6 h after injection. By 20–24 h and 30–35 h after injection progesterone concentrations had recovered to 4·63±0·94 and 14·07 ±4·17 ng/ml respectively (n = 6). Six out of seven ewes delivered prematurely 32·5± 2·9 h after injection. Delivery appeared to be normal, and was associated with increasing concentrations of 13,14-dihydro-15-oxo prostaglandin F2α in peripheral plasma. Concentrations of oestradiol-17β17β in peripheral plasma were slightly raised immediately before delivery, at which time progesterone concentrations were within the preinjection range. These data suggest that progesterone withdrawal is one mechanism that initiates increased prostaglandin F2α secretion in the pregnant sheep.

Regulation of ovine placental lactogen: lack of correlation with progesterone secretion

1982 ◽  
Vol 95 (2) ◽  
pp. 275-279 ◽  
Author(s):  
M. J. Taylor ◽  
G. Jenkin ◽  
J. S. Robinson ◽  
G. D. Thorburn
Keyword(s):  
Dehydrogenase Activity ◽  
Hydroxysteroid Dehydrogenase ◽  
Placental Lactogen ◽  
Peripheral Plasma ◽  
Significant Fall ◽  
Progesterone Secretion ◽  
Pregnant Sheep ◽  
Significant Change

After administration of an inhibitor of 3β-hydroxysteroid dehydrogenase activity to late-pregnant sheep, a sharp and significant fall in progesterone concentrations in peripheral plasma was noted, and lowered levels were sustained for up to 24 h. However, no significant change in the secretion of ovine placental lactogen (oPL) was noted. These results indicate that progesterone secretion does not regulate secretion of oPL during pregnancy.

β-Endorphin in sows during late pregnancy: effects of cloprostenol and oxytocin on plasma concentrations of β-endorphin in the jugular and uterine veins

1993 ◽  
Vol 136 (2) ◽  
pp. 199-206 ◽  
Author(s):  
J. E. Aurich ◽  
I. Dobrinski ◽  
N. Parvizi
Keyword(s):  
Opioid Peptides ◽  
Surgical Intervention ◽  
Physiological Function ◽  
Plasma Concentrations ◽  
Late Pregnancy ◽  
Oestrous Cycle ◽  
Maternal Circulation ◽  
Peripheral Plasma ◽  
Prostaglandin F

ABSTRACT β-Endorphin was measured in the plasma of pigs during late pregnancy and at different stages of the oestrous cycle. In pregnant animals, β-endorphin secretion from uteroplacental tissues into the maternal circulation and the possible effects of oxytocin and the prostaglandin F2α (PGF2α) analogue cloprostenol on β-endorphin release were determined. Plasma β-endorphin concentrations in pregnant sows were significantly higher than in non-pregnant pigs. However, there were no significant changes in β-endorphin values throughout the oestrous cycle. Because the increase in plasma β-endorphin concentrations had occurred before luteolysis and onset of labour it could not be attributed to the stress of parturition. The surgical intervention of a laparotomy increased β-endorphin release into peripheral plasma. Cloprostenol but not oxytocin caused an immediate increase in plasma β-endorphin concentrations. At parturition, endogenous PGF2α may be involved in the regulation of β-endorphin secretion. Concentrations of β-endorphin in the jugular and uterine vein plasma were not significantly different, and so it would appear that β-endorphin in the plasma of pregnant sows is not of uteroplacental origin. In conclusion, changes in the concentration of β-endorphin in peripheral plasma, associated with pregnancy but not the oestrous cycle, exist in pigs. Hence a physiological function of peripheral opioid peptides in the periparturient sow is feasible. Journal of Endocrinology (1993) 136, 199–206

Concentrations of progesterone and oestradiol-17β after administration of a 3β-hydroxysteroid dehydrogenase inhibitor to sheep in late pregnancy

1987 ◽  
Vol 113 (1) ◽  
pp. 97-101 ◽  
Author(s):  
M. J. Taylor
Keyword(s):  
Plasma Concentrations ◽  
Late Pregnancy ◽  
Hydroxysteroid Dehydrogenase ◽  
Premature Delivery ◽  
Plasma Progesterone ◽  
Twofold Increase ◽  
Rapid Fall

ABSTRACT An inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD) activity was administered to sheep in late pregnancy. A rapid fall in plasma progesterone concentrations followed, associated with premature delivery by all animals 44±3 h (s.e.m.) after administration of inhibitor. A significant (about twofold) increase in plasma concentrations of oestradiol-17β was detected immediately before delivery. These results demonstrate, in contrast to previous reports, that 3β-HSD inhibitors have the capacity consistently to induce premature delivery associated with increased oestrogen release in sheep. J. Endocr. (1987) 113, 97–101

Inhibition of progesterone secretion by a 3β-hydroxysteroid dehydrogenase inhibitor in late pregnant sheep

1985 ◽  
Vol 63 (2) ◽  
pp. 136-142 ◽  
Author(s):  
Graham Jenkin ◽  
Geoffrey D. Thorburn
Keyword(s):  
Hydroxysteroid Dehydrogenase ◽  
Placental Lactogen ◽  
Plasma Progesterone ◽  
Progesterone Secretion ◽  
Pregnant Sheep ◽  
Plasma Estradiol ◽  
Prostaglandin F ◽  
Essential Prerequisite ◽  
Estradiol 17Β

The role of progesterone in the initiation of parturition in the sheep is unclear. Whether a decrease in plasma progesterone is the essential prerequisite for the initiation of parturition or whether other factors also maintain uterine quiescence until delivery is not known. The effect of withdrawal of progesterone on the initiation of parturition has been investigated by intravenous administration of trilostane, a 3β-hydroxysteroid dehydrogenase Δ5−4 isomerase inhibitor, to late pregnant sheep. Twenty-five or 100 mg trilostane caused a precipitous decrease in plasma progesterone to about 30% of preinjection levels. Progesterone remained depressed for up to 7 days after treatment. 13,14-Dihydro-15-keto-prostaglandin F2α (PGFM) became elevated between 7 and 36 h after trilostane injection but gradually returned to preinjection levels during the subsequent 36 h, at a time when plasma progesterone was still depressed. Four of 11 animals treated with 100 or 200 mg trilostane aborted prematurely at a time when plasma PGFM was maximal and plasma progesterone minimal. There were no consistent changes in plasma estradiol-17β or ovine placental lactogen concentrations after treatment with trilostane. It is suggested that a decrease in plasma progesterone will cause a transient increase in plasma PGFM concentrations which can lead to the premature initiation of parturition. In some instances the myometrium does not appear to respond to the elevated PGFM concentrations even when the estrogen:progesterone ratio is elevated by a decrease in plasma progesterone.

FOETAL AND MATERNAL PLASMA CONCENTRATIONS OF 13,14-DIHYDRO-15-OXO-PROSTAGLANDIN F IN THE MARE DURING LATE PREGNANCY AND AT PARTURITION

1978 ◽  
Vol 78 (2) ◽  
pp. 201-215 ◽  
Author(s):  
R. J. BARNES ◽  
R. S. COMLINE ◽  
L. B. JEFFCOTT ◽  
M. D. MITCHELL ◽  
P. D. ROSSDALE ◽  
...  
Keyword(s):  
Plasma Concentration ◽  
Maximum Concentration ◽  
Plasma Concentrations ◽  
Late Pregnancy ◽  
Maternal Plasma ◽  
Premature Delivery ◽  
Rapid Rise ◽  
Second Stage ◽  
Prostaglandin F ◽  
Venous Plasma

SUMMARY The concentrations of 13,14-dihydro-15-oxo-prostaglandin F (PGFM), the stable metabolite of prostaglandin F, were measured in the plasma of catheterized mares and foetuses and non-catheterized thoroughbred mares and ponies during the last months of gestation. The plasma concentration of PGFM increased gradually towards term in all groups of animals. During the operation for insertion of catheters, maternal and foetal concentrations of PGFM were high, but the values fell to basal levels 24–48 h after the operation. It was found that preoperative starvation (24 h) led to a rise in the concentration oef PGFM in th maternal plasma. The raised concentrations of PGFM during the operation were associated with low progestogen and high oestrogen concentrations in umbilical venous plasma. The subsequent survival period of the catheterized foal was inversely related to the maximum concentration of PGFM attained during the operation. Changes in the plasma concentration of PGFM were studied during normal parturition in thoroughbred mares, during oxytocin-induced delivery in non-catheterized ponies and during premature delivery or abortion in the catheterized animals. The greatest increase in the concentration of PGFM was seen in the thoroughbred animals during second-stage labour; oxytocin also resulted in a very rapid rise in the level of PGFM, which remained high until delivery. In the catheterized animals, the birth of live foetuses was associated with a rise in the concentration of PGFM in both foetal and maternal plasma during the last 2 h before delivery. Less consistent changes were found during abortion.

Peripheral plasma progesterone concentrations in pregnant and non-pregnant greyheaded flying-foxes (Pteropus poliocephalus) and little red flying-foxes (P. scapulatus)

1995 ◽  
Vol 7 (5) ◽  
pp. 1163 ◽  
Author(s):  
PA Towers ◽  
L Martin
Keyword(s):  
Breeding Season ◽  
Plasma Concentrations ◽  
Late Pregnancy ◽  
Corpora Lutea ◽  
Flying Foxes ◽  
Plasma Progesterone ◽  
Peripheral Plasma ◽  
Pteropus Poliocephalus ◽  
In The Wild ◽  
Gas Chromatography Mass Spectroscopy

Blood was collected from breeding-season and pregnant P. poliocephalus females shot in the wild and from captive pregnant and ovariectomized P. poliocephalus and P. scapulatus females. Peripheral plasma progesterone concentrations measured by radioimmunoassay were similar to those obtained by gas chromatography-mass spectroscopy: in intact non-pregnant P. poliocephalus females without corpora lutea (CLs) values ranged from 2 to 30 ng mL-1; after ovariectomy, they ranged from 1 to 85 ng mL-1. A significant source of progesterone in these bats may be the adrenal. In P. poliocephalus, peripheral plasma progesterone concentrations showed relatively little change over the breeding season or in early pregnancy when a CL formed, but increased from mid pregnancy to reach 200-800 ng mL-1 in late pregnancy. A mid-pregnancy ovary with CL contained 2.80 ng progesterone whereas the contralateral ovary contained 0.13 ng. Overall, CL size decreased during pregnancy and was negatively correlated with plasma progesterone concentrations. In late pregnancy, the main source of progesterone appears to be the placenta; plasma concentrations increase with placental growth and are significantly correlated with placental weight, and placentas contain 4-8 micrograms progesterone g-1. There was no evidence that progesterone concentrations fall before parturition. Limited observations indicated that peripheral progesterone concentrations follow similar patterns in P. scapulatus.

Metabolism of [4-14C]estrone by sheep erythrocytes around the time of parturition

1976 ◽  
Vol 54 (7) ◽  
pp. 666-669 ◽  
Author(s):  
Charles P. W. Tsang
Keyword(s):  
Dehydrogenase Activity ◽  
Blood Cells ◽  
Phosphate Buffer ◽  
Incubation Medium ◽  
Late Pregnancy ◽  
Hydroxysteroid Dehydrogenase ◽  
Internal Standards ◽  
17Β Estradiol ◽  
Acetate Derivative

The metabolism of [4-14C]estrone in vitro by red blood cells of sheep in late pregnancy and after parturition has been studied. [14C]estrone (600 ng) was incubated with 0.5 ml erythrocytes plus 0.5 ml of Krebs–Ringer phosphate buffer, pH 7.4, for 2 h at 37 °C in an atmosphere of air. After incubation, [3H]estrogens were added to the incubation medium as internal standards for identification and for correction for procedural losses. Metabolites were isolated and purified by chromatography, acetate derivative formation, and recrystallization to a constant 3H/14C ratio. Approximately 20% and 2% of added estrone were converted to 17β-estradiol and 17α-estradiol, respectively. The remainder was recovered unchanged. Daily measurements of 17β-hydroxysteroid dehydrogenase activity in erythrocytes of five ewes, over the period 8 days prepartum to 4 days postpartum, showed no significant change in activity.

PARTURITION IN THE GOAT: PLASMA CONCENTRATIONS OF PROSTAGLANDIN F AND STEROID HORMONES AND UTERINE ACTIVITY DURING LATE PREGNANCY AND PARTURITION

1976 ◽  
Vol 68 (3) ◽  
pp. 383-389 ◽  
Author(s):  
I. UMO ◽  
R. J. FITZPATRICK ◽  
W. R. WARD
Keyword(s):  
Steroid Hormones ◽  
Plasma Concentrations ◽  
Late Pregnancy ◽  
Experimental Period ◽  
Significant Decline ◽  
Progesterone Concentration ◽  
Uterine Activity ◽  
Uterine Contractions ◽  
Prostaglandin F

SUMMARY Changes in plasma concentrations of hormones and uterine activity associated with spontaneous parturition in the goat were examined. No change in oestradiol-17β concentration was detected during the experimental period, but oestradiol-17α consistently increased in concentration 3–4 days before parturition. This was followed by an increase in prostaglandin F two days later, while a pre-partum decline in progesterone concentration occurred 18–20 h after the significant increase in prostaglandin F. The onset of uterine contractions coincided with a significant decline in progesterone concentration and a period of continually rising prostaglandin F and oestradiol-17α concentrations. Uterine activity expressed in Montevideo units did not change until 10–8 h before foetal expulsion. These results support the hypothesis that in the goat the elevated prepartum concentration of prostaglandin F brings about luteolysis and a subsequent decline in progesterone concentration.

THE EFFECTS OF DEXAMETHASONE AND INDOMETHACIN ON THE OUTCOME OF PREGNANCY IN THE RABBIT

1975 ◽  
Vol 64 (2) ◽  
pp. 363-370 ◽  
Author(s):  
J. R. G. CHALLIS ◽  
I. J. DAVIES ◽  
K. J. RYAN
Keyword(s):  
Late Pregnancy ◽  
Late Gestation ◽  
Premature Delivery ◽  
Progesterone Concentration ◽  
Dexamethasone Treatment ◽  
Similar Time ◽  
Plasma Progesterone ◽  
Peripheral Plasma ◽  
Prostaglandin F ◽  
Length Of Gestation

SUMMARY Pregnant rabbits were treated with indomethacin (8–10 mg/kg/day) or dexamethasone (1·2–1·8 mg/kg/day) during late gestation. The effects of these treatments on the concentrations of progesterone and prostaglandin F (PGF) in the peripheral plasma, and the outcome of gestation were studied. Treatment with indomethacin significantly prolonged the length of gestation (P < 0·01) compared with control, untreated animals. In these treated animals, the plasma progesterone levels declined at a similar time to that in control rabbits but the increase in systemic PGF normally seen during late pregnancy was reduced. Dexamethasone treatment reliably induced premature delivery within 3–6 days. The plasma progesterone concentration fell rapidly during the first 24 h of dexamethasone administration, but in no animal was this associated with a significant increase in the plasma levels of PGF. These results are consistent with the suggestion that prostaglandins are involved in the normal initiation of parturition in the rabbit. They do not support the hypothesis that the effect of dexamethasone on the length of gestation is mediated through an increase in the production of prostaglandin F.

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