Oestrogen Metabolism in Sheep Myometrium

Rossier, G; Pierrepoint, C. G.

doi:10.1530/jrf.0.0370043

Cited by 17 publications

(7 citation statements)

References 11 publications

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“…However, apart from being a pure biologically inactive excretion products, sulfoconjugated oestrogens may also serve as precursors for a local production of free oestrogens, depending on a tissue specific expression of an oestrogen sulfatase (OS). Such a ªsulfatase pathwayº was shown in ovine myometrium in late gestation (Rossier and Pierrepoint, 1974), or at pathological situations in human breast carcinoma tissue (Santner et al, 1984).…”

Section: Introductionmentioning

confidence: 84%

Investigations on the activity of bovine placental oestrogen sulfotransferase and -sulfatase from midgestation to parturition

Hoffmann

Falter²,

Vielemeier³

et al. 2001

Exp Clin Endocrinol Diabetes

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To gain further information on the biological role of the high amounts of conjugated estrone (E1S) secreted by the bovine placenta, an in vitro assay system was developed to measure oestrogen sulfotransferase (OST) and oestrogen sulfatase (OS) activities in caruncular and cotyledonary homogenates and the respective subcellular fractions. Placental tissue was obtained from 150 (n = 3), 220 (n = 4), 240 (n = 3) and 270 days (n = 3) pregnant and parturient cows (n = 4). 3H-E1 and 3H-E1S served as substrates and 4-nitrophenyl sulfate potassium salt was used as a competitive inhibitor to block OS when testing for OST activity. OST-activity did not change during pregnancy and parturition and was higher (p < 0.001) in cotyledonary than in caruncular tissue with mean conversions (median) of 61.8% and 41.6% after 30 min of homogenate incubation. On a subcellular level OST-activity was clearly associated with the cytosol. OS-activity was higher (p < 0.001) in caruncular than in cotyledonary homogenates; it was constant during pregnancy (median of conversion: 88.0% and 66.4%, resp.), but was significantly decreased (p < 0.05) at parturition (median of conversion: 48.1% and 30.6%, resp.). On a subcellular level in both the cotyledon and the caruncle highest OS-activities were detected in the microsomal and the mitochondrial fractions. The decreased placentomal OS-activities in parturient cows are inconsistent with a substantial role of OS in the prepartal increase of free oestrogens. These results also suggest that bovine placental oestrogens may largely exert their action locally within the placentomes during most time of gestation as the enzymes catalyzing sulfoconjugation (i.e. inactivation of free oestrogens) and desulfation (i.e. activation of conjugated oestrogens) are expressed in close proximity to each other. In this respect the finding of oestrogen receptors in caruncular stromal cells is of particular interest.

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Section: Introductionmentioning

confidence: 84%

Investigations on the activity of bovine placental oestrogen sulfotransferase and -sulfatase from midgestation to parturition

Hoffmann

Falter²,

Vielemeier³

et al. 2001

Exp Clin Endocrinol Diabetes

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“…It is possible that oestrone may be formed in the gravid uterus by an alternative pathway such as hydrolysis from a pool of un¬ conjugated oestrogens. Both the myometrium (Rossier & Pierrepoint, 1974) and the placenta (Pierrepoint, Anderson, Harvey, Turnbull & Griffiths, 1971;Findlay & Seamark, 1973;G. Jenkin, J. R. G. Challis & R. B. Heap, unpublished observations) contain appreciable sulphatase and sulphotransferase activity.…”

Section: Discussionmentioning

confidence: 98%

“…than f3H]oestrone infusions, suggesting that during the former experiments unconjugated oestrone was produced and released into the uterine vein. Experiments in vitro with ovine myometrium (Rossier & Pierrepoint, 1974) and placenta (see Findlay & Seamark, 1973) indicate that the equilibrium between oestradiol-17/? and oestrone in these tissues favours reduction.…”

Section: Discussionmentioning

confidence: 99%

The EXTRACTION OF OESTROGENS, AND THE RATE OF SECRETION OF OESTRONE AND OESTRADIOL-17β BY THE UTERUS IN THE PREGNANT SHEEP

Challis¹,

Harrison²,

Heap³

1974

Journal of Endocrinology

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The sharp increase in oestrone and oestradiol-17\g=b\production during the 48 h before parturition in the ewe does not always result in the uterine venous concentration of these steroids being greater than that found in peripheral blood, even though the gravid uterus is considered to be the major source of enhanced oestrogen synthesis in late pregnancy. This anomaly has been partly resolved by the results from tracer kinetic studies. During the infusion of labelled oestradiol-17\g=b\ or oestrone into a jugular vein to steady state, 53% of [3H]oestradiol-17\g=b\ and 62% of [3H]oestrone in the peripheral circulation were extracted by a gravid uterine horn. The extraction of [3H]oestradiol-17\g=a\, a product of the infused steroids, was 53% and 45% during the infusion of [3H]oestrone and [3H]oestradiol-1 7\g=b\,respectively.Calculations of the secretion rate of these steroids by one gravid horn, after correcting for uterine extraction, gave values that represented a substantial proportion of the kinetically determined production rate. This confirms that an appreciable part of the oestrogen produced just before term is in fact derived from the gravid uterus. However, the possibility that other sources may contribute to oestrogen synthesis in late pregnancy cannot be excluded. The findings show that a direct measurement of arteriovenous difference and uterine blood flow is inadequate to determine oestrogen secretion rates by the gravid uterus.

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“…The main oestrogen, oestrone sulphate, diffuses through the membranes of the chorionic vesicle to the uterus where it is deconjugated and reduced to biologically active oestradiol (Rossier & Pierrepoint, 1974). Such a local transfer may explain why the gravid uterine horn began to be active when attachment took place and why the non-gravid horn, when present, remained almost quiescent during the whole pregnancy, because very few placentomes are present in this location.…”

Section: Discussionmentioning

confidence: 99%

Pattern of electrical activity of the ovine uterus and cervix from mating to parturition

Garcia‐Villar¹,

Toutain²,

Ruckebusch³

1984

Reproduction

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The electrical activity of the uterus, greater curvature and lesser curvature, and of the cervix were recorded throughout several oestrous cycles, matings and the entire course of pregnancy in a set of ewes. In cyclic ewes, all electrode sites were active during the periovulatory period, but during the luteal phase only the cervix and lesser curvature continued to present regular activity, i.e. episodes of 6-8 min duration. Matings failed to disrupt the oestrous activity pattern in 5 out of 6 ewes. During the subsequent pregnancy in 4 ewes, activity, when present, consisted of the cyclic occurrence of regular activity episodes in the gravid horn(s) (greater curvature) and in the cervix (and lesser curvature in 1 ewe). Three phases were recognized on the basis of the activity of the greater curvature of the gravid horn(s). The first phase corresponded to quiescence of the horn from Day 5 (Day 0 = mating) to about Day 41. The second phase was marked by the sudden onset of regular activity of the uterus; frequency rapidly increased and maximal values were reached around Day 49, after which frequency progressively decreased until around Day 66. The third phase was characterized by a steady state in genital tract activity until the peripartum period. The cervix and lesser curvature activity followed an almost similar development of regular activity episodes with only slight time differences.

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Oestrogen Metabolism in Sheep Myometrium

Cited by 17 publications

References 11 publications

Investigations on the activity of bovine placental oestrogen sulfotransferase and -sulfatase from midgestation to parturition

Investigations on the activity of bovine placental oestrogen sulfotransferase and -sulfatase from midgestation to parturition

The EXTRACTION OF OESTROGENS, AND THE RATE OF SECRETION OF OESTRONE AND OESTRADIOL-17β BY THE UTERUS IN THE PREGNANT SHEEP

Pattern of electrical activity of the ovine uterus and cervix from mating to parturition

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