Estradiol and progesterone receptors in estrogen-primed endometrium

Hirsutism, virilism, polycystic ovarian disease, and the steroid-gonadotropin-feedback system: a career retrospective

This career retrospective describes how the initial work on the mechanism of hormone action provided the tools for the study of hirsutism, virilism, and polycystic ovarian disease. After excessive ovarian and or adrenal androgen secretion in polycystic ovarian disease had been established, the question whether the disease was genetic or acquired, methods to manage hirsutism and methods for the induction of ovulation were addressed. Recognizing that steroid gonadotropin feedback was an important regulatory factor, initial studies were done on the secretion of LH and FSH in the ovulatory cycle. This was followed by the study of basic mechanisms of steroid-gonadotropin feedback system, using castration and steroid replacement and the events surrounding the natural onset of puberty. Studies in ovariectomized rats showed that progesterone was a pivotal enhancer of estrogen-induced gonadotropin release, thus accounting for the preovulatory gonadotropin surge. The effects of progesterone were manifested by depletion of the occupied estrogen receptors of the anterior pituitary, release of hypothalamic LHRH, and inhibition of enzymes that degrade LHRH. Progesterone also promoted the synthesis of FSH in the pituitary. The 3α,5α-reduced metabolite of progesterone brought about selective LH release and acted using the GABA(A) receptor system. The 5α-reduced metabolite of progesterone brought about selective FSH release; the ability of progesterone to bring about FSH release was dependent on its 5α-reduction. The GnRH neuron does not have steroid receptors; the steroid effect was shown to be mediated through the excitatory amino acid glutamate, which in turn stimulated nitric oxide. These observations led to the replacement of the long-accepted belief that ovarian steroids acted directly on the GnRH neuron by the novel concept that the steroid feedback effect was exerted at the glutamatergic neuron, which in turn regulated the GnRH neuron. The neuroprotective effects of estrogens on brain neurons are of considerable interest.

Luteal cytoplasmic estradiol and progesterone receptors in human endometrium: in vitro fertilization and normal cycles

Luteal cytoplasmic estradiol (E2) and progesterone (P) receptor levels were measured from the 22nd to the 25th days of the menstrual cycle in endometrial samples obtained from seven patients in an in vitro fertilization (IVF) program who received no embryo replacement after ovarian stimulation with clomiphene citrate/human menopausal gonadotropin/human chorionic gonadotropin, and from seven normally menstruating women. Serum levels of E2, P, follicle-stimulating hormone, luteinizing hormone, and prolactin (PRL) were measured in blood samples collected at the time of biopsy. The E2 (P less than 0.01) and PRL (P less than 0.001) levels were higher in stimulated than in spontaneous cycles. The level of cytoplasmic P receptor was decreased in endometrium in stimulated cycles, but cytoplasmic E2 receptor remained unchanged. These alterations in the luteal phase of cytoplasmic P receptor in the endometrium could be involved in the low rate of success following the IVF program.

Immunohistochemical study of distribution of estrogen receptors in corpus and cervix uteri

An immunohistochemical assay based on monoclonal antiestrophilin antibodies has been used to localize estrogen receptor (ER) in frozen sections of normal human endometrial, myometrial and cervical tissues from menstruating, hormonally treated, pregnant and postmenopausal women. Specific staining was confined to the cellular nuclei. In proliferative phase endometrium, postmenopausal emdometrium, and endometrium from patients treated with hormone ERs were easily detected in most glandular and stromal cells. After ovulation and in early pregnancy a quick and distinct decrease of ER expression was noted. This was especially the case with the more superficial layers of endometrium (endometrium functionalis), the majority of whose cells had either weak localization of ER or none at all. In the endometrium basalis, however, the reduction of ER localization turned out to be more moderate. More then half of the epithelial and stromal cells displayed nuclear staining, partly strong. The myometrium of the corpus uteri showed a similar ER localization and dependence on hormonal stage when compared with the endometrium functionalis. The endocervical mucosa displayed a high degree of ER expression in the proliferative phase, in postmenopausal women and in women who had been treated with hormones. Unlike the endometrium and myometrium, the endocervical glands underwent minimal changes in nuclear ER content during the menstrual cycle. Although the endocervical stroma showed cyclic alterations in ER levels, their reduction after ovulation was less marked than in the corresponding endometria. In cervical squamous epithelium ER localization was predominantly confined to the basal layers. In the course of cellular maturation, specific nuclear staining vanished. In the proliferative phase, after the menopause and in early pregnancy, the basal, parabasal and intermediate cells were specifically stained. In the postovulatory phase, However, nuclear staining was confined to the basal and parabasal cells. Hormonally treated squamous epithelia almost completely lacked nuclear ER localization.

Detection of estrogen receptor mRNA in human uterus

We transcribed a cDNA clone of the human estrogen receptor (ER) with T7 RNA polymerase. The 32P-cRNA transcript complementary to ER mRNA was hybridized to poly(A)+ RNA from human uterus and revealed a single band of approximately 4.2 kilobases. No hybridization was seen with the cRNA probe of the opposite orientation. Hybridization of total RNA from calf and rat uterus yielded a single band at approximately 3.8 kilobases for both species. Total RNA from rat spleen did not hybridize. A 35S-labeled cRNA probe was prepared for in situ hybridization of ER mRNA in human uterus and spleen. Autoradiographic signal was present over endometrial epithelium, stromal cells of the lamina propria, and smooth muscle cells of the myometrium but was absent from sections of spleen. The ER mRNA hybridization label was located over cytoplasm and nuclei of uterine target cells.

Progesterone (P) receptor dynamics in estrogen primed normal human cervix following P injection

Progesterone (P) receptor levels were measured in the cytosol and in the 0.4 M KCl nuclear extract in human cervical tissues with [3H]-R5020 as a ligand and the results compared with those obtained in the myometrium and endometrium of the same uteri. Tissue samples were obtained from 28 women, grouped as follows: group A, 12 premenopausal controls; group B, 7 perimenopausal women who received estrogen 7 to 11 days before operation; and group C, 9 perimenopausal and postmenopausal women who received estrogen as in group B plus P injection 1 to 3 hours before operation. Estrogen administration resulted in a significant rise in total P receptor levels in the cervix, compared with the endometrium and myometrium. P injection after estrogen priming resulted in down-regulation of the P receptor in the cervix to undetectable levels, whereas in the endometrium and myometrium it resulted only in redistribution of the P receptor, with higher nuclear levels and lower cytosol levels. These results indicate the possibility of a different mechanism of regulation of the P receptor in the human cervix, compared with that in the endometrium and myometrium.

Relationship of plasma estradiol and progesterone levels to egg productivity in domestic chicken hens

Female chickens from eight different genetic stocks, ranging from 13 to 21 months of age, and exhibiting various levels of egg production were studied. Plasma samples were collected between 1700 and 2200 hr to determine basal circulating levels of progesterone (P4) and 17 beta-estradiol (E2) by radioimmunoassay. Linear regression analysis was used to describe the relation between mean hormone levels (E2, P4, and E2/P4) and mean egg production from these groups, and correlation coefficients were used to evaluate the general usefulness of these hormone parameters for estimating egg production within a group or flock of hens. Of the three hormone parameters evaluated, basal circulating E2/P4 was found to be the best estimator of egg productivity.

The protective role of progesterone in the prevention of endometrial cancer

An association between endometrial hyperplasia and corpus cancer has long been suspected. Genetically predisposed women are at greater risk of developing endometrial cancer if subjected to long uninterrupted period of estrogen stimulation. Endometrial cancer need not be inevitable if 14 day courses of an oral progestogen are continued for as long as is necessary; in some women, however, the lesions will progress and, therefore, should be carefully followed with repeated endometrial biopsies. Epidemiological evidence suggests a true link between unopposed estrogens and early, less invasive endometrial cancer, and progestogens appear capable of protecting against the development of cancer and hyperplasia, although complete protection has not yet been achieved. The protective action of progestogens is supported by the fact the none developed endometrial cancer in a series of 490 women of reproductive age who received continuous estrogens by way of pellet implants of 17 beta estradiol for conception control for 1--10 years. Evidence for the protective action of progestogens in estrogen-treated menopausal women was less solid than in non-menopausal women but was nonetheless considerable. Our study of 1058 women, 45 years of age and older, receiving continuous estrogens by way of 17 beta estradiol pellets over a period varying from 1 to 21 years, revealed that the incidence of cancer was not greater and was possibly less than that expected in an untreated population of menopausal women.

Estrogen-progestin pharmacodynamics of the postmenopausal endometrium studied by thymidine labeling

Five postmenopausal women were treated with conjugated equine estrogens, 1.25 mg tablets for 25 days, and medroxyprogesterone acetate, 10 mg tablets, in combination with the last 10 estrogen doses. Twenty-five endometrial biopsy specimens were incubated in vitro with tritiated thymidine and radioautographic slides were prepared. Within five days of estrogen treatment the thymidine labeling index (TLI) in both glands and stromal cells increased from a very low resting state to relatively high levels of DNA synthesis and cell proliferation. Within five days after addition of progestin, epithelial TLIs decreased to low levels and returned to minimal baseline levels four days after the last steroid dose. Analysis of variances indicated significant changes in epithelial cells (P less than 0.0001) confirming that the proliferative effect of estrogens was suppressed during the progestin phase. Stromal TLI changes were not significant (P = 0.46).