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PubMed1990

Alpha 1-adrenoceptor augmentation of beta-stimulated cAMP formation is enhanced by estrogen and reduced by progesterone in rat hypothalamic slices.

These experiments examined the influence of estradiol and progesterone given in vivo on norepinephrine (NE) regulation of cAMP synthesis in hypothalamic and preoptic area slices in vitro. Administration of progesterone to estrogen-primed female rats attenuated NE-induced slice cAMP accumulation. This hormone-dependent reduction in NE-stimulated cAMP synthesis was observed in slices incubated with TTX and in slices prepared from hypophysectomized rats, suggesting that progesterone effects on NE receptor activation of cAMP-generating systems are not secondary to the release of neurotransmitters that inhibit adenylyl cyclase or to changes in pituitary hormone secretion. Progesterone suppression of NE-induced cAMP formation could be prevented by incubating slices in the presence of a phorbol ester. In additional studies, the activity of beta-NE receptors was assessed by measuring isoproterenol (ISO)-stimulated cAMP accumulation in the presence of the phosphodiesterase inhibitor RO-20-1724, and the activity of alpha 1 receptors was evaluated by measuring phenylephrine (PHE) augmentation of the ISO response. Estradiol reduced the cAMP response to ISO in both hypothalamic and preoptic area slices, and this effect was not reversed by subsequent progesterone treatment. Estradiol also enhanced PHE augmentation of ISO-stimulated cAMP synthesis. Moreover, administration of progesterone subsequent to estradiol eliminated alpha 1-receptor augmentation of the ISO response. An alpha 1 enhancement of the ISO response is observed if the progestin receptor antagonist RU 38486 is administered before progesterone. Progesterone also abolished PHE potentiation of vasoactive intestinal polypeptide-stimulated cAMP accumulation. In contrast, neither phorbol ester nor muscarinic (carbachol) potentiation of the cAMP response to ISO was affected by progesterone. The data suggest that ovarian steroids regulate the coupling of both alpha 1 and beta receptors to the membrane effector systems that generate intracellular cAMP.

Animals↗

PubMed1990

[The effect of epidermal growth factor (EGF) with estradiol and progesterone on prolactin secretion from cultured human decidual tissues of early pregnancy].

Prolactin is now accepted as a normal product of the decidual cells of the human endometrium. We investigated the effect of epidermal growth factor (EGF) with estradiol and progesterone on prolactin secretion by the decidual tissues from the early pregnant endometrium. The decidual tissues were separated from villi, minced and cultured in collagen gel matrix with serum-free medium. Immunological staining of the cultured decidual tissues showed prolactin localization and EGF receptors on the stromal cells. Cultured media were collected every 2 days. The culture for the first 2 days was incubated with the serum-free medium alone (= preculture), and the following test culture was supplemented with/without additives. The prolactin content in cultured media was quantified by EIA. The results of the effect of steroid(s) and EGF were represented as a comparison of prolactin contents in the preculture and the test culture. An increase in prolactin secretion was found after the tissues were treated with a combination of 10(-8)M estradiol and 10(-6)M progesterone or 10(-6)M progesterone alone. After 8 days, the prolactin secretion rate increased about 3-fold over the precultured value. Estradiol alone kept the prolactin secretion at the precultured value. Prolactin secretion gradually decreased in the non-additive culture. These results indicate that progesterone was essential in the secretion of prolactin. Simultaneously, similar decidual tissues were incubated with a combination of EGF and steroid(s). The secretion of prolactin in the group treated with progesterone alone decreased dose-dependently responding to added EGF on the 8th day of culture. In the presence of estradiol and progesterone, the secretion rate decreased to the values similar to the progesterone alone group with the addition of 0.1, 1 ng/ml EGF, and the decrease in prolactin secretion was less with the addition of 10 ng/ml EGF. Mixed cultures of the decidual tissues and villi showed that the prolactin secretion rate increased in all groups treated with/without estradiol and/or progesterone. These results imply that progesterone derived from villi might control decidual prolactin secretion. The effect of high concentration EGF (50 ng/ml) on the prolactin secretion appeared similar to the isolated decidual tissues. These results suggest that decidual prolactin secretion is regulated by the combined effects of steroids and EGF.

Decidua↗

PubMed1990

Autoradiographic localization of [3H]RU 486 and [3H]progesterone in the uterus, pituitary and hypothalamus of the rat.

Twenty-one castrated oestrogen-primed Wistar rats, which were 2-months-old, were injected via the jugular vein with 100 microCi/100 g body weight of [3H]RU 486 or [3H]progesterone. Some of these received unlabelled compounds for competition studies. Samples of reproductive tract, pituitary and hypothalamus were excised after 15 min. The 4-micron frozen sections were processed for thaw-mounted autoradiography. The exposure time of the autoradiogram was approximately 6 months. After the injection of [3H]RU 486 and [3H]progesterone, the nuclear concentration of radioactivity was most distinct in muscular and stromal cells of the uterus, and the epithelial nuclei of lumina and glands showed weak labelling. Nuclear localization was also observed in muscle cells of the vagina, cervix and oviduct. After injection of [3H]progesterone, the radioactivity was found in the nuclei and cytoplasm of anterior pituitary cells and some cells showed a preferential nuclear concentration of radioactivity. The distribution of [3H]RU 486 in the anterior pituitary was more extensive than that of [3H]progesterone. In the hypothalamus, specific localization of [3H]RU 486 and [3H]progesterone existed in neurones accumulated in the preoptic nucleus, preoptic suprachiasmatic nucleus and the periventricular nucleus. No localization was found in the diaphragm. Pretreatment with RU 486, but not with dexamethasone, reduced the nuclear concentration of radioactivity of [3H]progesterone in the vagina, uterus, oviduct, pituitary and hypothalamus. The nuclear concentration of radioactivity after injection of [3H]RU 486 was also decreased by preinjection with progesterone. The autoradiographic results suggest that RU 486 and progesterone competed for the specific binding site (possibly a progesterone receptor) in the target cells at the levels of the uterus, pituitary and hypothalamus in vivo.

Animals↗

PubMed1990

Autoradiographic localization of [3H]RU 486 and [3H]progesterone in the uterus, pituitary and hypothalamus of the rat.

Twenty-one castrated oestrogen-primed Wistar rats, which were 2-months-old, were injected via the jugular vein with 100 mu Ci/100 g body weight of [3H]RU 486 or [3H]progesterone. Some of these received unlabelled compounds for competition studies. Samples of reproductive tract, pituitary and hypothalamus were excised after 15 min. The 4-microns frozen sections were processed for thaw-mounted autoradiography. The exposure time of the autoradiogram was approximately 6 months. After the injection of [3H]RU 486 and [3H]progesterone, the nuclear concentration of radioactivity was most distinct in muscular and stromal cells of the uterus, and the epithelial nuclei of lumina and glands showed weak labelling. Nuclear localization was also observed in muscle cells of the vagina, cervix and oviduct. After injection of [3H]progesterone, the radioactivity was found in the nuclei and cytoplasm of anterior pituitary cells and some cells showed a preferential nuclear concentration of radioactivity. The distribution of [3H]RU 486 in the anterior pituitary was more extensive than that of [3H]progesterone. In the hypothalamus, specific localization of [3H]RU 486 and [3H]progesterone existed in neurones accumulated in the preoptic nucleus, preoptic suprachiasmatic nucleus and the periventricular nucleus. No localization was found in the diaphragm. Pretreatment with RU 486, but not with dexamethasone, reduced the nuclear concentration of radioactivity of [3H]progesterone in the vagina, uterus, oviduct, pituitary and hypothalamus. The nuclear concentration of radioactivity after injection of [3H]RU 486 was also decreased by preinjection with progesterone. The autoradiographic results suggest that RU 486 and progesterone competed for the specific binding site (possibly a progesterone receptor) in the target cells at the levels of the uterus, pituitary and hypothalamus in vivo.

Animals↗

PubMed1990

Plasma progesterone in reindeer in relation to ovariectomy and hysterectomy.

Four semi-domesticated reindeer were ovariectomized and 3 both ovariectomized and hysterectomized, 30-70 days before expected parturition. Anaesthesia with etorphine/propyonylphenthiazine was followed by an increase in the plasma concentration of progesterone of peripheral blood. The concentration of progesterone returned to pre-anaesthetic values before ovariectomy. Ovariectomy did not result in any substantial change in the plasma progesterone concentration within an observation period of 35-120 min. Hysterectomy was followed by a marked decrease in peripheral plasma progesterone within 60 min. The progesterone concentration in ovarian venous blood was slightly higher than the jugular venous blood in 1 animal and 150 and 400 times higher in the 2 other animals examined. Thus, despite lack of marked changes of progesterone in jugular venous blood upon ovariectomy, it is concluded that the ovaries are a major production site of progesterone in pregnant reindeer. The progesterone in uterine venous blood was close to that in the jugular vein in 1 animal, and slightly higher in 2 others. This observation, and the maintenance of pregnancy in spite of ovariectomy in 2 out of 4 animals, point to the foeto-placental unit as an additional source of progesterone production.

Animals↗

PubMed1989

[Rapid determination of plasma progesterone. Its value in ovarian stimulation for in vitro fertilization].

Plasma Progesterone levels show definite variations during the periovulatory period of the superovulated cycle similar to those of the physiological cycle. The question arises whether the pattern of these variations is of significance with regard to the success rate of the IVF cycle. This prospective study was conducted with a rapid and highly sensitive radioimmunoassay of plasma progesterone labelled with Iodine 125. A total of 452 cycles were initiated in 328 patients (280 cycles using a clomiphene citrate-HMG regimen, 272 cycles using an association of LHRH analogues with HMG according to three different protocols). Ovarian response was monitored with sonography and rapid plasma radioimmunoassays of 17 beta-estradiol, progesterone and LH (in non-analogue cycles). Plasma progesterone in particular was assayed 17 hours before, at the time, and 7 hours after the administration of HCG. 10,000 UI IM for triggering ovulation. During the Clomiphene-HMG therapy when LH levels are instable, the plasma progesterone assay is highly discriminant between the beginning of a true LH peak (with concomitant rise of progesterone greater than 1 ng/ml, 15.7% of the cycles) and hectic variations of LH (no concomitant rise of progesterone, 4.3% of the cycles); the progesterone assay was also able to detect the occurrence of ovulation in 3 cycles without sensible variation of plasma LH (1.1% of the cycles). Pre- and post-ovulatory levels of plasma progesterone also demonstrate a prognosis significance with regard to the chances of success of the cycle, with all the different types of ovarian stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Progesterone and estradiol production by normal and preeclamptic placentas.

Placentas obtained from women with preeclampsia produce more thromboxane, a potent vasoconstrictor, and less prostacyclin, a potent vasodilator, than normal. Although the factors responsible for this are not known, steroids are known to affect eicosanoid production, and the placenta is a rich source of progesterone and estradiol. If placental steroids contribute to the imbalance of increased thromboxane/decreased prostacyclin in preeclamptic placentas, then their placental production might also be abnormal. The following study was performed to see whether the placentas of preeclamptic women produce progesterone or estradiol abnormally. Fresh human term placentas were obtained immediately after delivery from normal and mild preeclamptic pregnancies. Whole placental tissues (350 mg) were incubated for three hours. Samples were collected and analyzed for progesterone and estradiol-17 beta by radioimmunoassay. Progesterone production was significantly higher in preeclamptic than in normal placentas without the addition of a precursor and with the addition of pregnenolone sulfate as a precursor, but not with the addition of pregnenolone alone. Both normal and preeclamptic placentas converted pregnenolone sulfate into progesterone as efficiently as they converted pregnenolone into progesterone. Estradiol production rates were similar in both preeclamptic and normal placentas, regardless of whether dehydroepiandrosterone sulfate was added as a precursor. These data indicate that placentas of women with mild preeclampsia produce more progesterone than normal, probably because they contain more pregnenolone sulfatase and larger stores of endogenous cholesterol. Higher concentrations of progesterone in the preeclamptic placenta could contribute to lower prostacyclin production because progesterone inhibits placental prostacyclin production.

Dehydroepiandrosterone↗

PubMed1986

Differential phosphorylation of the progesterone receptor by insulin, epidermal growth factor, and platelet-derived growth factor receptor tyrosine protein kinases.

Purified preparations of insulin, epidermal growth factor (EGF), and platelet-derived growth factor (PDGF) receptors were compared for their abilities to phosphorylate purified hen oviduct progesterone receptors. The specific activities of all three peptide hormone-induced receptor kinases were first defined using a synthetic tridecapeptide tyrosine protein kinase substrate. Next, equivalent ligand-activated activities of the three receptor kinases were tested for their abilities to phosphorylate hen oviduct progesterone receptor. Both the insulin and EGF receptors phosphorylated progesterone receptor at high affinity, exclusively at tyrosine residues and with maximal stoichiometries that were near unity. In contrast, the PDGF receptor did not recognize progesterone receptor as a substrate. Insulin decreased the Km of the insulin receptor for progesterone receptor subunits as substrates, but had no significant effect on Vmax values. On the other hand, EGF increased the Vmax of the EGF receptor for progesterone receptor subunits as substrates. Phosphorylation of progesterone receptor by the insulin and EGF receptor kinases differed in two additional ways. 1) EGF-activated receptor phosphorylated the 80- and 105-kDa progesterone receptor subunits to an equal extent, whereas insulin-activated receptor preferentially phosphorylated the 80-kDa subunit. 2) Phosphopeptide fingerprinting analyses revealed that while insulin and EGF receptors phosphorylated one identical major site on both progesterone receptor subunits, they differed in their specificities for other sites.

Animals↗

PubMed1988

Modulation of the binding of progesterone receptor to DNA by polyamines.

Putrescine, spermidine, and spermine are a group of small organic cations, collectively known as polyamines. They are present in all living cells, and their levels are generally increased in tumor cells. Progesterone receptor is a gene-regulatory protein that plays a major role in gestation and in hormonal responsiveness of breast cancer. We studied the effects of putrescine, spermidine, 2 lower homologues of spermidine, N1- and N8-acetyl spermidines, spermine, and N1-acetyl spermine on the sedimentation profile and DNA binding of progesterone receptor from rabbit uterus. Progesterone receptor, prepared in hypotonic buffer, sedimented at the 7S region of sucrose gradients. In the presence of 1 mM putrescine, a part of the receptor was converted to a 5S form. In the presence of 1 mM spermidine or 0.25 mM spermine, the receptor was completely transformed to the 5S form. The DNA binding of the 7S form of progesterone receptor was 7 +/- 3%. After incubating this receptor with 1 mM putrescine, 1 mM spermidine, or 0.25 mM spermine, its DNA binding increased to 16 +/- 4, 37 +/- 3, and 44 +/- 5%, respectively. The structural specificity of polyamines in facilitating the DNA binding of progesterone receptor was examined by using two spermidine homologues. The first homologue with one methylene group less than that of spermidine was as effective as spermidine in transforming progesterone receptor. Removal of two methylene groups, however, had a dramatic effect in reducing the efficacy of the resulting molecule to the level of putrescine. Taken together, our results show that natural polyamines are capable of modulating the binding of progesterone receptor to DNA. Since progesterone receptor is associated with the hormonal responsiveness of human breast cancer, polyamine levels in tumor cells might play an important role in the gene-regulatory function of progesterone receptor.

Acetylation↗

PubMed1987

Regulation of sterol biosynthesis and of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in cultured cells by progesterone.

Treatment of rat intestinal epithelial cells in culture (IEC-6) with progesterone (10 micrograms/ml) caused a strong inhibition of cholesterol biosynthesis as indicated by a decreased incorporation of radiolabel from [3H]acetate. This inhibition was accompanied by an accumulation of radioactivity in an intermediate which coeluted with authentic desmosterol upon high performance liquid chromatography (HPLC). In addition, treatment of cells with progesterone caused lesser accumulation of radiolabel in products with retention times (RT) of 7.9 and 13.5 min on reverse-phase HPLC. The RT-13.5 compound was tentatively identified as cholesta-5,7,24-trien-3 beta-ol based on its relative retention and on its conversion to cholesterol upon incubation with untreated cells. The RT-7.9 compound was identified as 24 (S),25-epoxycholesterol (S-EC) based on its coelution with authentic S-EC and by its conversion to 25-hydroxycholesterol upon reduction with LiAlH4. Incubation of IEC-6 cells with chemically prepared S-EC resulted in dose-dependent suppression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity within 6 h (I50 = 0.3 microM). Pretreatment of cells with progesterone prevented this suppressive effect. No suppression of reductase activity was observed in progesterone-treated cells in spite of obvious accumulation of S-EC in amounts sufficient to effect regulation; instead, a 2-3-fold increase in 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity occurred within a 24-h period. Following the removal of progesterone from the culture medium, reductase activity declined rapidly over the next 6 h. However, IEC-6 cells could not metabolize S-EC, derived either endogenously or exogenously, during a similar time frame; nor did progesterone affect the uptake of exogenous S-EC by IEC-6 cells. These results show that although progesterone treatment of cultured cells promotes the synthesis of a natural oxysterol suppressor of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, the continued presence of progesterone prevents the regulatory action of S-EC. The unique nature of this interference is high-lighted by the observation that progesterone could not prevent the suppression of reductase activity by either 25-hydroxycholesterol or mevalonolactone.

Animals↗

PubMed1984

Human low density lipoproteins (LDL) in combination with cholesterol or cholesteryl linoleate as precursors for progesterone synthesis of human placenta in organ culture.

After preincubation of term placental tissue in organ culture for 24 h, progesterone synthesis is 2-3 fold lower than without preincubation. By adding human male serum proteins (MW less than 12,400), we obtained 2-3.5 fold lower tissue levels of progesterone. Serum proteins with high molecular weight (MW greater than 12,400) are postulated to facilitate progesterone release by binding free medium progesterone. In test series without preincubation, there are no significant (p less than 0.05) differences in progesterone formation in the presence of cholesterol (C), cholesteryl linoleate (CL), and LDL. In test series with preincubation, LDL causes a twofold increase in medium progesterone with C (0.1 and 1 mM) and CL (0.1 mM) in the presence of the low molecular weight serum protein (MW less than 12,400) solution. A decrease of 50% was obtained by 1 mM CL with/and without LDL. In culture medium containing high molecular weight serum proteins (MW greater than 12,400), 0.1 and 1 mM C and CL induce a twofold increase in progesterone production without any significant (p less than 0.05) differences between the single values. No further stimulation could be observed by LDL because there was sufficient LDL for maximal progesterone formation. In conclusion, LDL enhances the utilization of cholesterol and cholesteryl linoleate for progesterone production in term placenta. A lipoprotein cholesterol receptor is suspected.

Cholesterol↗

PubMed1980

Relationship of presence of progesterone receptors to prognosis in early breast cancer.

The presence of progesterone receptors was found to be associated with a favorable prognosis in 98 patients with primary breast cancer. The occurrence of metastases was 3.6 times less probable in patients with progesterone receptor-positive tumors than in patients with progesterone receptor-negative tumors. There was also an inverse relationship between the concentration of progesterone receptor and the frequency of metastases. However, there was no statistical correlation between frequency of local recurrences and progesterone receptor content of the tumor. In patients displaying clinical or histological criteria of gravity, the presence of progesterone receptors allowed us to define subgroups with good prognosis. Thus, in women with progesterone receptor-positive cancers, metastases had occurred at 18 months, in only 5% of the 39 Grade III cancers and in none of the 25 cases with invaded axillary nodes. Measurement of estradiol receptor (105 patients including the previous 98 patients) was found to be less effective for guiding the prognosis of early breast cancer. Combined evaluation of estradiol and progesterone receptors did not provide any more information than did the determination of progesterone receptor alone.

Adult↗

PubMed1995

[Accuracy of current rapid milk progesterone assays in comparison with a routine laboratory method].

Four current commercially available rapid milk progesterone assays (Cowside rapid tube kit [test No. 1], Hormonost-Schnelltest Milch [test No. 2], Hygia Diagnostic RPT Progesterone Test [test No. 3] and Target-Milch-Progesterone-Schnelltest [test No. 4]) for dairy cows were tested for their accuracy in comparison with the gynecological status on the one hand and by using an approved quantitative laboratory-bound assay on the other hand. Milk samples were taken from 23 dairy cows with behavioural oestrus. From 18 species with expected intermediate levels of progesterone milk probes were taken between day 3 and day 6 post insemination and also from 26 gravid cows. The clinically established gynecological status of the dairy cows correlated completely with their milk progesterone values investigated with the laboratory-bound EIA. In contrast the accuracy levels of the rapid progesterone kits differed. The accuracy of test No. 1 was 81% regarding all milk probes, whereas test No. 2 achieved 91%, test No. 3 73.5% and test No. 4 only 69.5%. Milk samples yielding low progesterone levels partly showed big differences. The highest rates of false semiquantitative classifications were recorded in milk samples with intermediate progesterone values. Test No. 2 was the only one with satisfactory results in this range. Milk samples yielding high progesterone values proved to be the best in all four assays.

Animals↗

PubMed1994

Serum progesterone for the exclusion of early pregnancy in women at risk for recurrent gestational trophoblastic neoplasia.

OBJECTIVE: To evaluate the utility of the serum progesterone level for discriminating pregnancy from gestational trophoblastic neoplasia. METHODS: Serum progesterone levels were measured in 61 women with histories of trophoblastic disease who developed a re-elevation in hCG during surveillance and underwent a work-up to differentiate pregnancy from gestational trophoblastic neoplasia. Progesterone levels were analyzed in the context of diagnostic outcome (pregnancy versus gestational trophoblastic neoplasia) to identify optimal threshold levels of progesterone to be used for classifying outcome. RESULTS: Of the 61 women, 37 proved to be pregnant and 24 had gestational trophoblastic neoplasia. Progesterone less than 2.5 ng/mL was predictive of trophoblastic malignancy, with a sensitivity of 83% (20 of 24 subjects were classified correctly as having gestational trophoblastic neoplasia) and a specificity of 95% (35 of 37 patients with progesterone levels at or above 2.5 ng/mL were correctly classified as pregnant). Progesterone of at least 10 ng/mL was associated with viable pregnancy in 97% of the cases. Furthermore, the progesterone level predicted outcome regardless of the serum hCG value. CONCLUSION: The serum progesterone level is useful for discriminating early pregnancy from gestational trophoblastic neoplasia.

Adolescent↗

PubMed1993

Regulation of progesterone during pregnancy in the cat: studies on the roles of corpora lutea, placenta and prolactin secretion.

The regulation of progesterone secretion and release by the corpus luteum and/or by the placenta in cats during pregnancy has been poorly studied and the relative roles of the corpus luteum and the placenta in the release of progesterone into the plasma is not well defined. It is generally assumed that after 40-45 days of pregnancy, circulating progesterone is mainly produced by the placenta and that after 45-50 days the corpus luteum is no longer necessary to maintain pregnancy, even if remnants of corpora lutea are detected in the ovaries during the following interoestrous period. In this study, the relative roles of the placenta and ovary in progesterone production after 30 days of pregnancy have been analysed in an attempt to define the role of progesterone in pregnant cats. Different experiments involved (1) analysis of the effects of an ovariectomy performed at 30 days of pregnancy, and of megestrol acetate supplementation on plasma progesterone during the second half of pregnancy, (2) analysis of the effects of an ovariectomy performed at 45 days on plasma progesterone production and on pregnancy and (3) analysis of the effects of an antiprolactin agent (cabergoline) at days 30 and 40 of pregnancy on progesterone secretion and pregnancy. These results were all compared with the normal plasma progesterone profiles during (a) pseudopregnancy and (b) pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2000

Progesterone regulates human telomerase reverse transcriptase gene expression via activation of mitogen-activated protein kinase signaling pathway.

Emerging evidence indicates that sex steroid hormones regulate telomerase in target tissues. We have reported that estrogen activates telomerase through transactivation of the telomerase catalytic subunit, human telomerase reverse transcriptase (hTERT). Progesterone usually antagonizes estrogen action in reproductive organs, but the effect on telomerase remains unclear. In this study, we examine the effects of progesterone on the gene expression of hTERT in breast and endometrial cancer cell lines expressing progesterone receptor. Progesterone significantly induced hTERT mRNA expression within 3 h after exposure. This transient effect peaked at 12 h and then decreased. In contrast, exposure to progesterone for > 48 h antagonized estrogen effects and inhibited the estrogen-induced activation of hTERT expression; the cyclin-dependent kinase inhibitor p21/Waf1/Cip1 plays an integral role in this inhibition. Thus, progesterone exerts diverse effects on hTERT mRNA expression in a time-dependent manner. We also found that the mitogen-activated protein kinase signaling pathway mediates both the short-term and long-term effects of progesterone on hTERT gene expression. These findings support the notion that hTERT gene is a target of both estrogen and progesterone.

Breast Neoplasms↗

PubMed1985

Effects of progesterone-impregnated sponge treatment on peripheral plasma hormone levels and fertility in the cyclic ewe.

Cyclic ewes were treated with 500-mg progesterone-impregnated sponges for the synchronization of oestrus. In the first experiment, the sponges were removed from 79 ewes at intervals over a 17-day treatment and the residual amount of progesterone was measured in order to assess the rate of absorption of the hormone from the sponges by the animals. The residual progesterone was found to decrease linearly with the duration of sponge insertion but there was also a significant quadratic component indicative of a slowing down in the rate of progesterone absorption towards the end of the treatment period. In the second experiment, 13 cyclic ewes were treated with 500-mg progesterone sponges for 17 days and the eight ewes in oestrus following spongewithdrawal were mated. The peripheral plasma progesterone was assayed at intervals during sponge insertion and at weekly intervals after sponge withdrawal. The residual progesterone levels on the sponges and the plasma progesterone levels of the treated ewes were examined in relation to their oestrous response and fertility. There was a significantly higher residual level of hormone remaining on sponges from ewes that mated than on sponges from those that did not (P < 0.01). The 13 ewes exhibited luteal phase levels of plasma progesterone when assayed during the period of sponge insertion regardless of their response to treatment. The mated, fertile ewes had significantly higher plasma hormone levels than the non-mated and the mated infertile ewes, after sponge withdrawal.

Journal Article↗

PubMed1985

Pregnancy rates relative to recipient plasma progesterone levels on the day of nonsurgical transfer of frozen/thawed bovine embryos.

A total of 71 synchronized dairy heifers (Holstein Friesian x German Black Pied) were used as recipients of seven-day old frozen/thawed bovine embryos. Plasma progesterone concentrations and corpus luteum quality on the day of nonsurgical transfer (= day 7) were determined and related to pregnancy rates or estrus intervals in nonpregnant recipients. A total of 32 recipients (45.1 %) maintained pregnancy; 39 recipients (54.9 %) did not. No significant differences could be detected between progesterone levels in recipients that remained pregnant (3.14 +/- 0.24 ng/ml; x +/- SEM ) and those that did not maintain pregnancy (3.23 +/- 0.28 ng/ml). Optimal progesterone levels were between 2 and 5 ng/ml coinciding with a pregnancy rate of 51.1 % (24 47 ). Pregnancy rates apparently were decreased when progesterone levels were below 2 ng/ml (35.3 %; 6 17 ) or above 5 ng/ml (28.6 %; 2 7 ). Hence, optimal progesterone levels were identical to those for freshly collected embryos reported previously by Remsen et al. (1). Bovine corpus luteum quality graded by rectal palpation was related to some extent to progesterone levels but not to pregnancy rates. Out of 39 nonpregnant recipients seven animals (17.9 %) with a mean plasma progesterone level of 3.76 +/- 0.72 ng/ml showed an extended estrus interval of more than 55 days, probably indicating early embryonic mortality. Progesterone levels did not significantly differ between nonpregnant recipients with estrus intervals of various length. Plasma progesterone levels at the time of transfer are of limited diagnostic value for screening recipients prior to transfer of frozen/thawed embryos.

Journal Article↗