Cervical ripening after treatment with prostaglandin E2 or antiprogestin (RU486). Possible mechanisms in relation to gonadal steroids.

OBJECTIVE: To compare the mechanisms for cervical ripening after treatment with prostaglandin E2 or antiprogestin (RU486) to spontaneous cervical ripening, with focus on gonadal steroid receptors. STUDY DESIGN: Cervical biopsies were obtained from postpartal women after treatment with prostaglandin E2 (n=10), or antiprogestin (n=5). Postpartal women after spontaneous cervical ripening (n=10) served as controls. Levels of estrogen and progesterone receptors, their mRNAs, insulin-like growth factor I mRNA and serum estradiol and progesterone were quantitated. The collagen concentration and solubility by pepsin were determined. Statistical tests used were Kruskal-Wallis and Mann-Whitney U test. RESULTS: After prostaglandin E2 treatment the collagen concentration was higher (P<0.05) as compared to spontaneous ripening. After antiprogestin treatment the estrogen receptor concentration was higher (P<0.05) in comparison to spontaneous ripening. CONCLUSION: The elevated estrogen receptor concentration after antiprogestin treatment, in contrast to spontaneous ripening, and prostaglandin E2 treatment, indicates a that a receptor-mediated progesterone withdrawal does not explain the events behind spontaneous cervical ripening at parturition.

Hormonal regulation of the estrogen receptor in primary cultures of hepatocytes from female rats.

Estrogen treatment affects the hepatic synthesis and/or secretion of several proteins involved in clinically important pathological processes such as atherosclerosis, hypertension, and thrombosis. The endocrine regulation of the estrogen receptor (ER) concentration in primary cultures of rat hepatocytes was studied. Human growth hormone (hGH) and dexamethasone (DEX) in combination increased ER concentration 6-fold and ER mRNA levels 2.5-fold. These effects were not significantly different from those observed after treatment with the purely somatogenic bovine growth hormone (GH) in combination with DEX. Treatment with the lactogen ovine prolactin in the presence or absence of DEX did not significantly affect ER or ER mRNA concentrations. Triiodothyronine treatment at the most effective concentration (50 nM) increased ER and ER mRNA levels twofold. Medium supplementation with estradiol (0.1 nM) throughout the experiment did not affect the response to treatment with hGH and DEX. Treatment with high concentrations of ethinylestradiol in combination with hGH and DEX, however, increased the ER level twice as much as hGH and DEX without addition of estradiol or ethinylestradiol, whereas the ER mRNA concentration was the same in both the GH+DEX group and GH+ DEX+ (estradiol or ethinylestradiol) groups. These data indicate the importance of GH in combination with glucocorticoids for the maintenance of ER concentrations in the rat liver. Thyroid hormones may be of some, although minor importance, whereas the data suggest that prolactin is not directly involved in hepatic ER regulation.

Potential roles for gonadal steroids and insulin-like growth factor I during final cervical ripening.

OBJECTIVE: To determine whether gonadal steroids and insulin-like growth factor I influence the final cervical remodeling during parturition. METHODS: Cervical biopsies were obtained transvaginally before labor (n = 10) and after spontaneous cervical ripening and vaginal delivery (n = 20). Levels of estrogen and progesterone receptors, their messenger RNAs, insulin-like growth factor I messenger RNA, and serum estradiol and progesterone were measured. Collagen and proteoglycan concentrations and compositions were measured to estimate the degree of cervical ripeness. RESULTS: The concentrations of estrogen and progesterone receptors decreased in comparison with the clinically unripe cervix before labor. The median estrogen receptor concentration (range) decreased from 10 (2-18) to 4.5 (2-14) fmol/mg protein (P < .01), and the progesterone receptor concentration from 105.5 (32-153) to 74 (30-115) fmol/mg protein (P < .05), whereas their messenger RNA levels were unchanged. The insulin-like growth factor I messenger RNA concentration declined from 16.1 (8.4-20.4) at term to 8.9 (1.5-18.5) amol/microgram DNA after parturition (P < .01). The collagen solubility by pepsin increased, but not significantly, and the collagen concentration was unchanged. The concentration of small proteoglycans, mainly decorin, decreased from 1.59 (1.20-1.97) to 0.84 (0.24-1.41) micrograms/mg wet weight (P < .001), and the concentration of versican increased, but not significantly (P = .07). CONCLUSION: Concentrations of estrogen and progesterone receptors and insulin-like growth factor I messenger RNA were decreased significantly after spontaneous cervical ripening in comparison to levels before labor. These changes coincided with a tendency toward increased collagen solubility and a decline in concentration of small proteoglycans, which probably alters collagen organization, thus allowing for cervical softening and dilation. These observations suggest that gonadal steroids influence the final cervical remodeling during parturition, an influence perhaps mediated by insulin-like growth factor I.

Cervical ripening in humans: potential roles of estrogen, progesterone, and insulin-like growth factor-I.

OBJECTIVE: During pregnancy in humans a gradual connective tissue remodeling takes place in the cervix. The aim of this study was to examine a possible relationship between the action of gonadal steroids and growth factors and the biochemically identifiable changes in connective tissues during cervical ripening. STUDY DESIGN: Cervical biopsy specimens and serum samples were taken from 20 term pregnant and 20 nonpregnant menstruating women. Estrogen receptors and progesterone receptors were measured with enzyme immunoassays. The messenger ribonucleic acid levels for estrogen receptors, progesterone receptors, and insulin-like growth factor-I were determined by solution hybridization with human complementary deoxyribonucleic acid probes. The concentration of collagen and its solubility by pepsin digestion were measured. Statistical evaluations were done with the Student t test. RESULTS: In term pregnancy the estrogen receptor level decreased to 14% and the progesterone receptor level to 24% of nonpregnant levels (p <0.001 and p <0.01). The insulin-like growth factor-I messenger ribonucleic acid level increased 400% (p <0.01), whereas the messenger ribonucleic acid levels for estrogen receptors and progesterone receptors were unchanged. The changes coincided with a twofold decrease in collagen concentration (hydroxyproline) and a twofold increase in collagen solubility. CONCLUSION: Estrogen receptors and progesterone receptors are present in human cervix. A significant down-regulation of estrogen receptors and progesterone receptors and a fourfold increase in the insulin-like growth factor-I messenger ribonucleic acid level were registered in term pregnant cervix. These findings coincided with the remodeling of the cervical connective tissue.

Regulatory effects of growth hormone, glucocorticoids, and thyroid hormone on the estrogen receptor level in the rat liver.

The multihormonal regulation of the estrogen receptor in the liver of female rats was studied under in vivo conditions. The steroid receptor level was assayed by hormone binding and specific mRNA analyzed by solution hybridization using a 35S-labeled RNA probe complementary to the ligand-binding domain of the estrogen receptor gene. Serum growth hormone levels were measured and correlated to the effects of glucocorticoid and thyroid hormone administration on the estrogen receptor expression. In animals subjected to adrenalectomy plus thyroidectomy, the estrogen receptor concentration was reduced from 59 fmol/mg cytosol protein to 10 fmol/mg protein (i.e., with 87% relative to control animals). Adrenalectomy or thyroidectomy alone caused a decrease with 14% and 66%, respectively. Substitution with 10 micrograms betamethasone and 1 microgram triiodothyronine daily for 9 days completely restored the receptor content to control levels. Substitution with either hormone alone increased, but only partially restored receptor levels. The effect of betamethasone alone was dose dependent from 10 micrograms/d to 100 micrograms/d. This dose dependence was not seen when the animal simultaneously received 1 microgram of triiodothyronine. Superphysiologic doses of triiodothyronine did not raise estrogen receptor levels above those seen in animals treated with physiologic doses. High doses of triiodothyronine (greater than 20 micrograms/d) decreased serum growth hormone levels. The estrogen receptor mRNA levels in livers from hypophysectomized animals were increased after treatment with growth hormone (2.5-fold), thyroid hormone (two-fold), and glucocorticoids (1.5-fold). The results obtained indicate a very complex regulation of liver estrogen receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

The estrogen receptor in the rat kidney. Ontogeny, properties and effects of gonadectomy on its concentration.

Estrogens have been suggested as modulators of the conversion of 25-hydroxyvitamin D3 to dihydroxylated compounds in the kidney. In order to further explore this hypothesis the estrogen-binding components in the kidney were studied in adult and immature rats. The basal receptor levels in adult animals were 9.6 fmol/mg protein (female) and 21.9 (male). The receptor-ligand complex had a Kd of 0.7 nM. Furthermore, the kidney receptor displayed similar characteristics as those of the cytosol liver estrogen receptor in terms of sedimentation properties on sucrose gradients, isoelectric focusing and ligand binding specificity. The ontogeny of cytosol high affinity estrogen binding sites was elucidated in female and male animals. Detectable levels of receptors (5 fmol/mg protein) were found during the first postnatal week in both sexes. During days 22-25 receptors reached maximum concentrations at about 30 fmol/mg protein. In the male this level then remained relatively constant throughout the time of study (60 days), whereas in the female the concentration decreased gradually over a period of 12-15 days to a basal level of 10 fmol/mg protein. A temporal study on the short- and longterm effects of ovariectomy on the concentration of estrogen binding sites in the kidney cytosol was also carried out. Shortly after gonadectomy (2-12 h) no effect was detected. During 20-48 h after the operation a 75% increase in the receptor level was seen. The results indicate a multihormonal control of the estrogen binding protein in the kidney similar to that seen in the liver. Furthermore, the data suggest that estradiol down-regulate its own receptor. The results are discussed in relation to present concepts on the actions of estrogens and the metabolism of vitamin D3.

Effects of thyroid hormones on the receptor level in estrogen target organs.

The influence of thyroid hormones on the turnover of cytoplasmic estrogen receptors in the liver, kidney and uterus of intact and ovariectomized female rats was studied under in vivo conditions. Thyroidectomy had no significant effect on the receptor level in the uterus but caused a substantial reduction of the receptor content in the liver and kidney. In livers of intact and ovariectomized animals receptor values were reduced with 70 and 80%, respectively, 30 days after thyroidectomy. Substitution with triiodothyronine (T3) restored the hepatic estrogen receptor concentration in thyroidectomized rats to the preoperative level. If rats that had been both ovariectomized and thyroidectomized were substituted with thyroid hormone for the same time period, the receptor level was increased but did not reach the level seen in animals that had been ovariectomized only. The effects of thyroid hormone substitution was found to be dose dependent and paradoxical. Thus, a high dose of 50 micrograms/day of triiodothyronine given to intact animals for nine days caused a 30% reduction in the hepatic receptor content. The same level of reduction was seen in the ovariectomized rat given a hormone dose of only 1 micrograms/day. When this type of rats was treated with the higher dose of triiodothyronine the reduction in hepatic estrogen receptors was 50%. These results are discussed in relation to existing information concerning the multihormonal regulation of estrogen receptor concentration in the rat liver.

Different regulation of the concentration of estrogen receptors in the rat liver and uterus following ovariectomy.

Data concerning the short- and longterm effects of ovariectomy on the levels of estrogen binding sites in the rat uterus and liver are presented. The information increases the understanding of the regulation of estrogen receptor synthesis. The circulating estrogen level is suggested to affect receptor synthesis in the uterus and liver differently. Shortly after gonadectomy (2--20 h), an elevation in the concentration of cytoplasmic binding sites in the uterus of 35% was observed, whereas no effect was seen in the liver cell. A longer period of time after ovariectomy (2--3 months) caused a reduction in the number of uterine receptor sites by 74%, whereas in the liver an increase of 84% was detected.