Uterine Progesterone Research Articles

The progesterone content of rabbit uterine flushings.

A detailed study has been made of the progesterone content of uterine flushings taken from rabbits of different endocrine states. A high content of progesterone was recovered from the uterine lumen of pregnant and pseudopregnant rabbits. The amount of progesterone recovered in the flushings was not simply dependent on the concentration in the plasma, because plasma progesterone concentrations rose before detection of progesterone in the flushings and remained high after uterine progesterone content had fallen. Progesterone did not appear in the uterine fluid unless uterine protein was present. This was particularly evident in rabbits treated with progesterone in which, despite abnormally high plasma concentrations, little progesterone was found in uterine fluid until the protein content increased. After treatment of rabbits with oestrogen at the time of ovulation, uterine progesterone was present in higher amounts concomitant with an elevation of protein content although the peak values of progesterone and protein were delayed by 2--3 days. Plasma progesterone concentrations of about 5 ng/ml were necessary before progesterone appeared in the uterine lumen.

In vitro and in vivo enhancement of progesterone binding to the uterine progesterone receptor by cortisol.

In vitro and in vivo enhancement of progesterone binding to the uterine progesterone receptor by cortisol.

The effects of ovariectomy and strech on the regulatory profile and activity of the uterus

Following ovariectomy of five New Zealand white rabbits at day 25 of pregnancy, the intrauterine pressure (IUP) and uterine progesterone (P) and prostaglandin (PG) levels were measured sequentially at days 25, 26 and 27. At day 25, when the uterine P and PGE and PGF were high, massive intrauterine treatment with 500 μg PGF2α provoked only a sustained contracture on which only low level oscillation in IUP was superimposed. At day 26, when the P levels had decreased significantly (P<0.001) and the PG levels had not changed significantly, 50 μg PGF2α significantly increased cyclic IUP as compared with the day 25 value (P<0.001). At day 27, when the P levels decreased further, as little as 5 μg PGF2α provoked still higher cyclic IUP, in spite of a significant reduction in PG levels (P<0.05). Stretching the uterus of six post partum and six 26 days pregnant rabbits (after removing the uterine contents) significantly increased the uterine PGF levels (P<0.001). However, stretch increased only cyclic IUP of the post partum uterus and was without effect on the pregnant uterus, which still had high P levels. These results indicate that the myometrium is activated by exogenous PG or stretch, regardless of whether the uterine PG levels increase, remain unchanged or even moderately decrease, provided that the uterine P levels are reduced to a critical value.

HORMONAL CONTROL OF PROGESTERONE RECEPTORS*

Uterine progesterone receptors are under dual hormonal control. Estrogen increases the concentration of receptor through a mechanism that depends on synthesis of both RNA and protein. Progesterone decreases the concentration of its own receptor, probably by enhancing its inactivation rate. This regulation explains receptor variations during the estrous cycle. In both guinea pig and rat uteri, cytosol receptor concentration is maximal at the preovulatory period and decreases after ovulation. Nuclear receptor was measured in the rat. Its concentration is also maximal at proestrus, but the higher nuclear to cytosol receptor ratio was observed at metestrus. There is a good correlation (r = 0.78) between nuclear receptor concentration, on one hand, and the product of cytosol receptor concentration times the plasma progesterone concentration, on the other hand. Autoradiographic studies show that receptor variations during the estrous cycle occur simultaneously in all cell types of uterine horn, cervix, and vagina, which suggests that similar mechanisms control receptor concentration in all of these cells. Progesterone receptor was also measured during pregnancy in rat uterus. Cytosol receptor concentration is low at the beginning of pregnancy (approximately 6000 binding sites per cell), declines slightly on Day 5 (approximately 4000 binding sites per cell), and then increases progressively during the remainder of pregnancy to attain its highest value on Day 22 (26,000 binding sites per cell). Nuclear receptor concentration is very low on Day 3 (1200 binding sites per cell), increases slightly on Day 5 (1900 binding sites per cell), decreases on Day 6, and then increases again to attain a plateau between Days 9 and 15 (approximately 2600 binding sites per cell). Thereafter, its concentration begins to decrease rapidly. On Day 22, the mean concentration is very low (700 binding sites per cell); in some animals (probably on the verge of parturition), no nuclear receptor can be detected.

Uterine activity and plasma progesterone levels in pregnant goats

Uterine activity was recorded during the last few weeks of pregnacy in goats, and related to changes in plasma progesterone concentration. In six of the 14 pregnancies, there was little activity until immediately pre-partum, but the remainder showed a progressive increase in uterine motility, particularly during the last seven days of pregnancy. There was a significant correlation between increased uterine activity and decline of peripheral plasma progesterone levels.

Interaction of uteroglobin with progesterone, 5alphapregnane-3,20-dione and estrogens.

Uteroglobin was obtained from 5 day pregnant rabbits and purified to homogeneity by Sephadex G 75 and DEAE-cellulose chromatographies. Progesterone binding to uteroglobin was decreased by lyophilization and enhanced by SH-reducing agents. Dithiothreitol was more effective than dithioerythritol, and beta-mercaptoethanol was only active at 25 to 100 mM concentrations. SH-blocking agents (iodoacetate, iodoacetamide, phydroxymercuribenzoate and, dithiobisnitrobenzoic acid) inhibited binding. In the absence of SH-reducing agents only one in every 500 uteroglobin molecules bound the hormone, whereas under optimal conditions (20 mM dithiothreitol) one in every two molecules bound progesterone. There was no significant difference in equilibrium dissociation constants under these two conditions. Uteroglobin had a relatively high affinity for progesterone (KD=4.1 X 10(-7)M) but a threefold higher affinity for 5alpha-pregnane-3,20-dione (KD=1.3 X 10(-7)M). Estradiol was bound but non-specifically with a very low affinity, and its binding was not enhanced by SH-reducing agents. Hormonal specificity of binding to uteroglobin was different from that of binding to rabbit uterine progesterone receptor. Various synthetic progestagens (chlormadinone acetate, norethisterone, R5020) were bound to the latter but not to the former protein. Diethylstilbestrol had some affinity (15% of that of progesterone) for uteroglobin and no affinity for the progesterone receptor. Uteroglobin incubated in the presence or absence of cofactors (NADH and NADPH) with or without dithiothreitol did not metabolize progesterone.

Uterine norepinephrine levels as related to plasma and tissue progesterone in pseudopregnant rabbits.

Pseudopregnancy was induced in rabbits by a single iv injection of 100 IU of human chorionic gonadotrophin (hCG). Uterine norepinephrine, located exclusively in adrenergic nerves, was markedly reduced (fluorometric determinations) during the first 6 days of pseudopregnancy and then returned towards pre-injection values. Plasma progesterone (measured by radioimmunoassay) was found to be elevated at days 3,6, and 12 of pseudopregnancy as compared to the very low values of the untreated controls. Although tissue progesterone also increased during pseudopregnancy (fourfold at day 6), there was a somewhat paradoxical relationship between plasma and tissue progesterone. In spite of unchanged plasma levels, tissue progesterone decreased considerably between days 6 and 12. The uterine/plasma progesterone ratio was very high (approximately 28) in non-pregnant (control) animals and ranged between 1 and 3 during pseudopregnancy. These results suggest that there is a causal relationship between the high levels of progesterone in the uterus and the reduced amount of norepinephrine transmitter in the adrenergic nerves in this organ, and that plasma progesterone concentration and the changing progesterone receptor levels regulate uterine progesterone concentration.

Clinical experience with the uterine progesterone system (Progestasert ®)

A new bioactive intrauterine contraceptive device of T-configuration releasing 65 mcg of progesterone daily for one year was studied in 115 multiparous and 35 nulliparous women. A total of 1,598 women months were accumulated. Three pregnancies, of which two were ectopic, occurred corresponding to 2.1 pregnancies per 100 women years. The continuation rate was 84.4 regarding the multiparas and 80.2 for the total material. Intermenstrual spotting or bleeding constituted the major reasons for removals. The presence of the system has resulted in a significant decrease of the amount of menstrual flow. Furthermore, dysmenorrheic pain and premenstrual cramps in those cases where they were present before insertion, have shown significant reduction during the observation period. Our preliminary results indicate that, at least with regard to multiparous women, Progestasert constitutes a conceivable alternative to other bioactive IUDs and further evaluation of this system should be encouraged.

Electrocardiographic Changes Induced by Insertion of an Intrauterine Device and Other Uterine Manipulations

A prospective study was carried out in normal women in order to investigate the effects of the following procedures on the electrocardiogram and blood pressure: (1) insertion of an intrauterine device (IUD)--the Lippes loop, Tcu-200, uterine progesterone system or Cu-7; (2) endometrial biopsy; and (3) uterine flushing. In groups in which a large IUD like the Lippes loop and/or a stiff IUD like the Cu-7 was inserted, the frequency of bradycardia was significantly higher than in any other groups. The severity of the bradycardia was similar in all of the groups and the frequency of this alteration was also similar among the nulliparous women or in those who complained of pain during the instrumentation, irrespective of the type of IUD inserted or the procedure carried out. No alarming modifications of blood pressure were observed and maintaining the patients in the recumbent position was sufficient to alleviate symptoms. In severe cases use of the Trendelenburg position should be enough to correct any alterations.

Purification of human uterine progesterone receptor

IT is now generally accepted that before the physiological response to the androgens1, oestrogens2, glucocorticoids3 and progesterone4–7 can be manifested, these hormones must complex with specific receptors in their target tissue. Since progesterone is important both in the mechanisms associated with transport of the ovum through the oviduct8,9 and in preparing the endometrium for implantation of the blastocyst10, a greater understanding of the action of the hormone–receptor complex at the molecular level will lead to a more detailed knowledge of the mechanisms involved in reproductive biology. This understanding may be utilised to develop new contraceptive methods and to investigate the genesis and treatment of endometrial adenocarcinoma.

Plasma progesterone and oestrogens in sheep during late pregnancy: contribution of the maternal adrenal and ovary.

Summary. Levels of progesterone were determined by competitive protein-binding techniques and oestrogens by radio-ligand binding techniques in the uterine and peripheral plasma of parturient ewes. Uterine progesterone levels began a continuous decline 4 to 5 days ante partum whereas jugular levels only declined 1 or 2 days ante partum. Peripheral plasma progesterone levels were significantly elevated in ewes carrying multiple fetuses compared to those in ewes with a single fetus. A similar but non-significant difference existed in the uterine plasma. Adrenalectomized and adrenalectomized-ovariectomized ewes had lower progesterone levels in the peripheral blood but not lower uterine levels than did control ewes. Ovariectomy did not affect progesterone levels. Oestrone and oestradiol values were lower in the uterine venous concentrations of adrenalectomized and adrenalectomized-ovariectomized ewes. A depression of oestrogen values before birth was not noted in ovariectomized ewes. It is concluded that the maternal adrenal has a definite rôle in oestrogen biosynthesis in pregnant sheep.

Receptors for progesterone

Coordinated estrogen- and progesterone-induced changes regulate biological functions of the endometrium. The uterine deciduoma reaction is used as a model in defining the mechanism of the progesterone-induced endometrial transformations. Uterine progesterone concentrations were determined by radioimmunoassay during three critical periods related to progesterone action: the preparatory period, the initiatory period, and the proliferative period. Tissue progesterone concentration significantly exceeded peripheral plasma concentration during the late afternoon of proestrus and in pseudopregnant animals on the day of maximal sensitivity to deciduoma induction. On the basis of the uterine progesterone concentration at the time of trauma, it was possible to predict whether or not decidualization would occur. Thus, substantiation was obtained for the existence of a specific uterine progesterone receptor, and its presence was related to prior exposure of the uterus to estradiol-17β. Summarized evidence for the existence of specific progesterone binding proteins in uterine tissue from several mammalian species, including the human being, shows a fair degree of uniformity in the properties of these binding proteins, e.g., tissue specificity, ligand specificity, and sensitivity to estrogen stimulation. Although some questions remain as to whether the effectiveness of progesterone therapy in endometrial adenocarcinoma can be considered as being proportional to the degree of resemblance of the cancer to normal endometrium, it is suggested that the possibility of such a relationship makes highly desirable the organization of programs designed to correlate the presence of progesterone receptor with progesterone responsiveness in these tumors.

Progesterone and corticosterone binding in rabbit uterine cytosols.

The steroid hormone-binding proteins in rabbit uterine cytosols and blood plasma have been investigated. Uterine cytosols prepared from ovariectomized estrogen-primed animals contained a 7.8S “receptor” which bound progesterone but not corticosterone. A 4.3S progesterone- and a 4.1S corticosterone-binding protein were also present in the cytosols. Rabbit blood plasma contains a protein (CBG) which binds both progesterone and corticosteroids and has a sedimentation coefficient of about 4S. The possibility that the cytosol corticosterone binder was derived from blood present in the estrogen-stimulated uterus was investigated by in situ perfusion. However, the moles of corticosterone binding sites read from Scatchard plots were found to be the same in cytosols from either perfused or unperfused uteri. The intrinsic association constant of the high affinity rabbit progesterone receptor calculated from Scatchard plots was 7.8 ± 0.7 × 108M-1. In the presence of 0.3M KC1 the 7.8S progesterone receptor appeared to dissociate into 4S subunits, in agreement with reports from other laboratories. However, Scatchard plots of equilibrium dialysis data revealed a loss of high affinity binding in the presence of KCl, and a 4S subunit was not seen on recentrifugation of isolated 8S receptor in sucrose gradients containing 0.3M KCl. The properties and behavior of the uterine progesterone receptor are very similar in at least two species, the rabbit and the guinea pig. (Endocrinology93: 74, 1973)

Progesterone in uterus and plasma. VI. Uterine progesterone receptors during the estrus cycle and implantation in the guinea pig.

The concentration of the progesterone cytosol receptor in the uterus shows marked variations during the estrus cycle. It is maximum in proestrus (about 40,000 binding sites per cell) and falls progressively during estrus and postestrus to attain a 16-fold lower value in diestrus. The receptor has a sedimentation coefficient (measured by sucrose gradient centrifugation) of 6.7 S during proestrus. In estrus, 6.7 S and 4.5 S binders are present, and the 4.5 S binder is predominant in postestrus and finally found exclusively in diestrus. One cannot differentiate 3 and 7 day pregnant animals by the concentration and the sedimentation coefficient of the progesterone receptors from the corresponding non-pregnant guinea pigs. Thus the implantation takes place at a moment when the concentration of receptor is very low, suggesting that implantation is controlled by progesterone secreted previously (perhaps in the pre-ovulatory period). The concentration of progesterone receptor in the uterus is positively controlle...

Progesterone metabolism by uterine tissue of pregnant rats

The amount of progesterone metabolized during one hour incubations of uterine tissue from pregnant rats was determined. A tenfold increase in metabolic activity was observed between day 11 and day 21 of pregnancy when the results were expressed as nanograms of progesterone metabolized per gram of tissue per hour. A seventyfold increase was observed in the same period when the results were expressed in terms of nanograms of progesterone metabolized per whole uterus per hour. The major products were identified as 5α-pregnane-3,20-dione and 3a-hydroxy-5α-pregnan-20-one. Administration of luteinizing hormone and estrone in midpregnancy significantly increased the rate of in vitro progesterone metabolism by the uterus. Administration of progesterone and prolactin afer day 18 prevented normal parturition and significantly decreased the rate of in vitvo progesterone metabolism by the uterus. The results suggest a possible relationship between the progesterone-reducing activity of the rat uterus and uterine progesterone concentration during pregnancy, and suggest an effect of several hormones on uterine enzyme activity.

Uterine progesterone metabolism and progestational response: effects of estrogens and prolactin.

The effects of estrone (lμg/day) and prolactin (200 μg/day), alone and in combination, on deciduomal growth in response to uterine trauma and on uptake and metabolism of pi'ogesterone by nontraumatized uteri have been investigated in ovariectomized, progesteronetreated (2 mg/day) rats. Estrone significantly increased the size of traumatized uteri, whether administered during the 3-day period of uterine sensitization, immediately before traumatization, or during the 3-day period of deciduomal growth, immediately after traumatization. Prolactin significantly increased the size of traumatized uteri in the absence of estrone, but, when administered in the presence of estrone, significantly decreased the stimulatory effect normally produced by estrone. Both estrone and estradiol increased the uptake of progesterone by isolated uterine strips, but these increases could be accounted for entirely on the basis of the uterotrophic effects of the steroids and were not evident when expressed per mg uterine weight. Ne...

Progesterone and 20-alpha-hydroxypregn-4-en-3-one in plasma, ovaries and uteri during pregnancy in the rat.

Progesterone and 20α-OH-P levels were measured by double isotope assay in pregnant rat peripheral plasma, ovaries, uteri and placentae at selected times extending from the 2nd day of pregnancy until term. Evidence is presented which supports the conclusion that uterine tissue is capable of concentrating pro-gesterone above peripheral blood levels throughout early and midpregnancy. High intrauterine concentrations of progesterone relate quantita-tively to biological events associated with hormon al function, e.g., nidation, decidua formation and myometrial quiescence. Increased uterine motility, resulting eventually in parturition, apparently follows a reduction in uterine proges-terone concentration. These correlations cannot be made with the closely related progesterone metabolite, 20α-OH-P. This is likely due, in part at least, to its more rapid clearance from systemic compartments. (Endocrinology 87: 43, 1970)

An examination of the quantitative relationship between progesterone and the maintenance of pregnancy.

Peripheral plasma, placental and uterine progesterone concentrations were determined in pregnant rats and were related to the effects of ovariectomy and placental dislocation on the maintenance of pregnancy. Pregnancy maintenance correlated more closely with uterine than plasma progesterone levels, a distinction readily made following ovariectomy. During late pregnancy a uterine progesterone concentration of 2 μg/lOOg seemed sufficient to prohibit the development of parturient activity, although at midpregnancy higher uterine levels appeared necessary for the protection of fetal life. Fetal survival was critically dependent upon the gestational age at the time of ovariectomy and was linked either to a compensatory placental hypertrophy or to retention of the placentae of prematurely discharged fetuses. Under conditions in which pregnancy was maintained in ovariectomized rats, plasma, but not placental or uterine, progesterone dropped below normal preparturient levels. Adequate progesterone substitution th...