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ABSTRACT
The effect of continuous oestrogen treatment on uterine weight, and on cytoplasmic and nuclear oestrogen receptors was examined in rabbits. Modulation of the effects of oestrogen by progesterone was also studied. Uterine weight increased successively after exposure to oestrogen from 1 to 6 days. The concentration of both cytosolic and nuclear oestrogen receptors decreased in almost parallel fashion, however, irrespective of whether it was expressed per μg protein or μg DNA. Treatment with progesterone 5 days after oestrogenization caused no significant change in uterine weight at first. The oestrogen receptor concentration in both cytosolic and nuclear fractions decreased after 1 day but increased again after 3 days of progesterone treatment. The results indicated that there is a reduction in the actual concentration of oestrogen receptors in both cytosolic and nuclear fractions after continuous oestrogen treatment. The antagonism by progesterone of the effects produced by oestrogen appears to be transitory in nature, at least in the rabbit uterus.
J. Endocr. (1987) 115, 199–203
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ABSTRACT
Exposure of fetuses to some hormonally active agents may imprint permanent changes on the action of related hormones. These changes can be detected in adulthood as a modification of the degree of responsiveness to hormone action. The present study describes the effect of prenatal androgenization on the various responses to oestrogen in different types of cells in the uterus of prepubertal rats. Prenatal androgenization completely abolishes oestrogen-induced hypertrophy of uterine luminal and glandular epithelium, while it does not interfere with hypertrophy of circular myometrium and potentiates uterine eosinophilia and oedema. This dissociation between the various responses to oestrogen suggests that prenatal androgenization does not equally affect all uterine cell types.
Journal of Endocrinology (1989) 120, 379–384
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SUMMARY
Progesterone treatment significantly altered the response of the mouse uterus to oestradiol-17β. Oestradiol given alone produced many mitoses in the luminal and glandular epithelia but not in the connective tissue stroma. After treatment with progesterone this pattern was reversed and oestradiol produced many mitoses in the stroma but few in the epithelia. Production of stromal cell division was influenced by the dose of progesterone and by the period of treatment; a single day of treatment greatly reduced the numbers of epithelial mitoses produced by oestradiol but did not greatly increase stromal mitosis. At least 3 days' treatment was necessary for a maximal stromal response.
Doses of oestradiol sufficient to inhibit implantation and deciduomata production did not reverse the stromal response but did overcome, in part, the progestational suppression of epithelial mitosis, producing large numbers of mitoses in the luminal but not in the glandular epithelium.
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Department of Hormone Physiology, Imperial Cancer Research Fund, Lincoln's Inn Fields, London, WC2A 3PX
(Received 19 February 1975)
Oestrogen treatment in vivo increases the metabolism of progesterone by the rat uterus in vitro (Armstrong & King, 1971; Howard & Wiest, 1972). However, the pattern of metabolites produced is dependent on the concentration of progesterone used in vitro (Saffron, Loeser, Haas & Stavely, 1974). When high concentrations of progesterone were used, oestrogen increased both ring A and C20-ketone metabolism. At low concentrations oestrogen increased C20-ketone metabolism, whereas ring A metabolism was decreased.
This present experiment was carried out to see whether oestrogen affected uterine metabolism of progesterone in vivo in mice (Clark, 1973, 1974) in the same way.
[1,2,6,7-3H] Progesterone (5 or 500 pg; sp. act. 261 μCi/μg, Radiochemical Centie, Amersham) was injected intraluminally into both uterine horns of spayed mice 1 or 6 days after oestrogen priming as described by
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SUMMARY
Progestational agents were studied for their effects on collagenolytic activity and loss of collagen and wet weight from the involuting post-partum rat uterus. Administration of very large doses of progesterone (80–150 mg/day) significantly retarded uterine involution and loss of collagen. This was accompanied by a significant reduction in uterine collagenolytic activity. By 72 h post partum, uteri of rats treated with 150 mg progesterone/day had wet weights 30% above, collagen 85% above, and collagenolytic activity 45% below, those of the control uteri.
Similar effects were produced by 17α-acetoxy-6α-methylprogesterone at the same dosage levels. However, the progestational agent 6α-chloro-17α-acetoxypregna-4,6-diene-3,20dione acetate had no effect in this system.
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SUMMARY
A single injection of oestradiol given to ovariectomized mice pretreated with progesterone for several days stimulates a large increase in cell division in the uterine stroma which reaches a maximum 24 hr. later. A second injection 48 hr. after the first, also stimulates stromal cell division, but a second injection 12–36 hr. after the first does not. This failure to respond is not due simply to depletion of the stock of cells ripe for division. Rather it appears that the uterus becomes insensitive to further stimulation for approximately 36 hr. Although a second injection 24 hr. after the first injection does not increase stromal cell division, it does lengthen the refractory period so that a third injection given at 48 hr. has no effect.
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SUMMARY
The amounts of prostaglandins F2α (PGF2α) and E2 (PGE2) produced by homogenized, incubated, pregnant and non-pregnant guinea-pig uteri were compared. The sizes of the corpora lutea from these animals were considered in relation to the amounts of prostaglandins produced by their uteri.
The amount of PGF2α produced by the uteri from day-15 bilaterally pregnant guinea-pigs was significantly less than that produced by uteri from guinea-pigs on day 15 of the oestrous cycle. Corpora lutea from the pregnant animals were maintained but those from the day 15 non-pregnant animals had regressed. There was no significant difference between the results obtained for PGE2. Results from day 15 unilaterally pregnant animals and day 25 bilaterally pregnant animals are also presented and their implications discussed. The findings reported here may well explain how, in the guinea-pig, the conceptus is able to neutralize the luteolytic effects of the uterus.
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In view of the well-known species differences in the realm of reproductive physiology it would be a great advantage if an animal were found whose uterine muscle reacted in a manner similar to that of the human subject. It would make investigations of dosage of hormones and of hormone therapy of uterine muscle distinctly easier. Apart from some work on the activity of the Fallopian tubes of monkeys by Seckinger & Corner [1923] in vitro, and by Westman [1929] in vivo, no investigation of the movements of the monkey uterus in vivo has been noted by Reynolds [1939] in a very comprehensive review. The present work was carried out on the most readily available monkey, the rhesus monkey. Unfortunately, well-grown specimens are difficult to get from the dealers; the animal is also rather expensive for any routine investigation. Until its possibilities have been explored, however, its usefulness cannot be defined.
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SUMMARY
Uterine alkaline phosphatase and β-glucuronidase activity were assayed during the first 8 days of pregnancy in rats after unilateral tubal ligation and section. The results were as follows. Alkaline phosphatase increased in the pregnant horn from days 5 to 8 while the activity of the nonpregnant horn remained unaltered. This enhanced phosphatase activity was localized exclusively at the implantation sites. β-Glucuronidase steadily decreased during the first 8 days of pregnancy in both the gravid and non-gravid horns. The occurrence of a 'peak' in β-glucuronidase activity during the oestrogen surge on day 4 of pregnancy reported previously by Prahlad (1962) was not observed.
The results are discussed in relation to an interaction between the implanting blastocyst and the hormonally conditioned uterus.
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SUMMARY
In mated guinea-pigs one uterine horn was rendered sterile by ligation of the oviduct 2 or 3 days after finding spermatozoa in the vaginal smear. Two glass beads were inserted into the sterile horn on each of days 3–12 and on day 14 in experimental animals but not in controls. At autopsy on day 20 large corpora lutea were present in both ovaries of the control animals. The presence of beads that had been introduced on days 3 and 4 and on days 10–14 resulted in marked regression of the corpora lutea in the adjacent ovary, in the absence of a decidual reaction in the uterus, while luteal enlargement typical of pregnancy occurred in the contralateral ovary. Beads inserted on days 5–8 caused decidualization in the sterile horn but did not induce premature luteal regression in the ipsilateral ovary.
