Plasma binding of oestradiol in progesterone-treated rats

Progesterone treatment of female rats causes an increase in body weight possibly via suppression of oestradiol secretion. This study was carried out to investigate the effect of progesterone on the non-protein bound and hence presumably biologically active fraction of oestradiol. Oestradiol binding to plasma proteins was studied in female Wistar rats during the oestrous cycle and after 12 days of treatment with progesterone (5 mg/day). There was no change in either the unbound fraction of oestradiol or plasma albumin concentrations during the oestrous cycle. Plasma oestradiol concentrations in progesterone-treated rats were similar to those seen during dioestrus, as were the degree of oestrogen binding and the plasma albumin concentrations. Although it was not feasible to calculate unbound concentrations, these results suggest that the increased body weight seen in progesterone-treated rats, and also during pregnancy, may be a result of suppression of unbound oestradiol concentrations to levels similar to those occurring during dioestrus.     

Changes of progesterone content of rat uterine flushings in relation to serum concentrations of progesterone during the oestrous cycle.

Uterine fluid was collected from four-day cyclic rats at each stage of the oestrous cycle and assayed for progesterone and protein content. Progesterone was determined by radioimmunoassay either after ethanol (or 2.5% NaOH) denaturation of proteins from uterine flushings ('total' progesterone) or without protein denaturation ('ether-extractable' progesterone). The amount of 'ether-extractable' progesterone in the lumen was constant from metoestrus to pro-oestrus (340 pg per uterus) but lower in oestrus (200 pg per uterus). However, 'total' progesterone content of uterine fluid was subject to cyclic variations and was highest in dioestrus (890 pg per uterus) and lowest in oestrus (350 pg per uterus), in contrast to serum progesterone which is lowest in dioestrus and highest in oestrus. Protein content of uterine flushings peaked to 780 micrograms per uterus in pro-oestrus then fell to about 140 micrograms per uterus until the end of the oestrous cycle. Changes in protein content of the lumen were followed by qualitative variations since the mean amount of 'bound' progesterone ('total' progesterone minus 'ether-extractable' progesterone) released per milligram of denatured lumen protein rose from 1.8 pmol in pro-oestrus to 18.2 pmol in dioestrus. The changes of luminal 'bound' progesterone during the oestrous cycle suggest that progesterone binding to luminal proteins could be an important modulator of progesterone action in rat uterus. Moreover, the variations in progesterone content of the lumen, irrespective of serum progesterone concentrations, are consistent with the hypothesis that progesterone synthesis occurs in the uterus.     

Changes in the density of peripheral benzodiazepine binding sites in genital organs of the female rat during the oestrous cycle

The affinity and the density of peripheral-type benzodiazepine binding sites (PBzS) in tissues from the genital organs of female rats were studied during the oestrous cycle. When comparing PBzS density on the day of oestrus to PBzS density on the day of pro-oestrus, a significant increase was observed in the ovary (1.9-fold), oviduct (2.4-fold) and uterus (1.7-fold), but not in the kidney. Serum oestradiol also increased to a maximum on the day of pro-oestrus. The ovarian and uterine PBzS density and serum concentrations of oestradiol and progesterone were measured every 8 h between the days of dioestrus and pro-oestrus. Ovarian and uterine PBzS density increased to a maximal value at 01:00 and 09:00 h, respectively, on the day of pro-oestrus. However, a significant increase in PBzS density occurred in the ovary (P less than 0.02) and uterus (P less than 0.001) at 09:00 h on the day of pro-oestrus as compared to 09:00 h on the day of dioestrus. These changes were associated with an increase in serum oestradiol and progesterone concentrations. The affinity of PBzS in all tissues examined remained unaltered during the oestrous cycle. This study demonstrates that changes associated with the oestrous cycle occur in the density of PBzS in various genital organs.     

The mature mid-cycle follicle in the mare.

Oestrogen and progesterone concentrations in blood and follicular fluid and blood levels of LH were determined in 426 mares at different stages of the oestrous cycle. Mature follicles occur at all stages of the cycle; they ovulate readily in early metoestrus, occasionally in late metoestrus and very rarely in dioestrus. Maturation of a mid-cycle follicle is associated with intermediate levels of LH, which are less than those found during oestrus. This lower level of LH together with a high level of progesterone are probably responsible for the failure of ovulation and regression of most of the mid-cycle mature follicles found in the mare.     

Changes in rat ovaries of specific binding for LH, FSH and prolactin during the oestrous cycle and pregnancy.

In cyclic rats, the highest ovarian specific binding for LH was 6-0+/- 2-2% inpro-oestrus. During pregnancy, the specific binding of 125I-labelled bovine LH by rat ovaries increased gradually and reached a maximum of 24-1+/-4-9% between Days 14 and 18 of gestation; a slight decrease in binding was observed at Day 20 of pregnancy. Ovarian specific binding for FSH was also highest in pro-oestrus (8-9+/-2-1%), decreasing to about 50% in oestrus and metoestrus, but staying relatively constant during pregnancy. For prolactin, the specific binding in rat ovaries was highest (7-1+/-1-6%) in pro-oestrus, quite high in metoestrus and dioestrus and low in oestrus. Specific binding increased gradually only after Day 14 of pregnancy. Serum concentrations of rat LH, FSH and prolactin at different stages of the oestrous cycle and during pregnancy were determined by radioimmunoassays, and no obvious correlation was observed between levels of circulating hormones and the specific binding of these hormones in ovarian tissues. Affinity constants (Ka) for the hormones were very similar between ovaries from pro-oestrous rats and late-pregnant rats, being 0-31 X 10(9) M-1 for LH, 0-65 X 10(10)M-1 for FSH, and 1-14 X 10(10)M-1 for prolactin. Increases in specific binding for different hormones were due to increases of total binding sites in the ovary under different physiological states.     

胶原酶-3活性在大鼠动情周期及胚泡着床中的变化(英文)

大鼠动情周期以及胚胎着床过程中,子宫内膜会发生结缔组织的降解与重构。胶原酶3（MMP－13）是降解纤维类胶原的主要蛋白水解酶类之一。其活性在这些过程中的变化值得研究。采用液体闪烁计数测定~3H标记胶原的方法,对大鼠动情周期及早期妊娠子宫中胶原酶-3（MMP－13）的活性进行了测定。结果表明：在动情周期中;激活型MMP－13在间情期最低,酶原型及激活型的MMP－13在动前期达高峰,动情后期酶原型和激活型MMP也明显高于间情期（P＜0.05）（Fig．1）。妊娠第1、2天酶原型的MMP-13的活性显著高于第3～7天,第3、4天酶原型和激活型MMP-13的活性均低于妊娠第1、2天（P＜0.05）;而第5天酶原型MMP-13的活性却显著高于第4、6两天（P＜0．05）;激活型MMP－13的活性也高于第4天（P＜0．05）（Fig．2）。着床部位酶原型MMP－13的活性明显高于非着床部位（P＜0．05）,而激活型MMP－13的活性则无明显差异（P＞0．05）（Fig．3）。大鼠假孕早期子宫中MMP－13的活性变化与正常早期妊娠相似,但其活性却明显低于正常早期妊娠（Fig．4）。结果提示：大鼠子宫中MMP-13参与大鼠动情周期及早期妊娠过程,尤其是在胚胎着床过程中可能起着重要作用。     

Changes in the concentration of high-affinity oestradiol receptors in rat uterine supernatant preparations during the oestrous cycle, pseudopregnancy, pregnancy, maturation and after ovariectomy

A quantitative method was used to determine the concentration of high-affinity oestradiol-receptor sites in rat uterine supernatant preparations under various physiological conditions. Cyclic changes in concentration were observed during the oestrous cycle, with a maximum occurring in late dioestrus. The changes followed a similar pattern in endometrium and myometrium, although concentrations were higher in the former. In pseudopregnancy the concentration was initially low, rising to a maximum on the tenth day. In early pregnancy a high concentration of receptor was found to be associated with the developing placenta, but this declined in later stages of pregnancy. After ovariectomy or combined ovariectomy and adrenalectomy the receptor concentration remained at a constant low value that could be increased by treatment with oestradiol. The receptor concentration was considerably higher in immature than in adult uteri.     

Oestradiol and progesterone: soluble receptor levels and metabolism in the uterus of the ovariectomized ewe

Ovariectomized ewes received injections designed to mimic to some extent oestradiol and progesterone secretion during early pregnancy (maintenance progesterone), during oestrus (oestrous oestradiol) and during the luteal phase of the previous cycle (priming progesterone). The animals were killed at times equivalent to 1, 4 or 7 days after oestrus in those animals which had received oestrous oestradiol. The level of soluble oestradiol and progesterone receptors in whole uterus, and [3H]oestradiol and [3H]progesterone metabolism by uterus minces were measured. Oestradiol receptor level was highest on day 1 in those animals receiving oestrous oestradiol with no significant effect at any stage of the inclusion or omission of priming or maintenance progesterone. Progesterone receptor level was also high on day 1 in those animals receiving oestrous oestradiol with high levels maintained to day 4. Again, inclusion of priming or maintenance progesterone was without effect. In animals not receiving oestrous oestradiol the level of both receptors was uniformly low. Metabolism of [3H]oestradiol was low and not affected by treatment. [3H]Progesterone metabolism, although more variable, was also low and not affected by treatment.     

The nature of the sex-linked differences in glutathione peroxidase activity and aerobic oxidation of glutathione in male and female rat liver

1. Glutathione peroxidase activity in the livers of sham-operated female rats was about 60% higher than in similarly treated male rats. The value in the ovariectomized female was about the same as that in the castrated or sham-operated male. 2. Glutathione peroxidase activity changed during the oestrous cycle. The highest value was in oestrus, and was about 50% higher than the lowest activity, which was found in dioestrus. The activity in proestrus and in metoestrus was respectively about 20 and 30% higher than in dioestrus. 3. In the pregnant female 1 or 2 days before term, glutathione peroxidase activity was about 20% higher than that in the female in oestrus. 4. Subcutaneous implants of both oestra-diol and progesterone in the gonadectomized rats increased the glutathione peroxidase activity approximately to the values found in the female at oestrus. 5. The rate of aerobic oxidation of GSH in the female rat liver was about 80% higher than in the male and about 110% higher than in the gonadectomized rats. Treatment of gonadectomized rats with subcutaneous implants of oestradiol and of progesterone increased the rate of oxidation of GSH by about 100%. 6. In the presence of azide the rate of GSH oxidation in the male and in the female was respectively about 3.5- and 2.1-fold that in the absence of azide. In castrated or ovariectomized rats the increase due to the presence of azide was about 2.4-fold. In the gonadectomized rats treated with oestradiol or progesterone the rate of GSH oxidation in the presence of azide was about 2.2-fold that in its absence. 7. The rate of lipid peroxidation in female was 15-30-fold that in male or in gonadectomized rats. Treatment of the gonadectomized rats with oestradiol or with progesterone increased the rate of lipid peroxidation up to values that were even higher than in the female. In the presence of GSH the formation of malonaldehyde from peroxides was virtually eliminated. 8. The results suggest that the sex-linked differences in glutathione peroxidase activity, in the rate of GSH oxidation and in the rate of lipid peroxidation are due to the female sex hormones. 9. It is suggested that both the catalase activity and the rate of hydrogen peroxide formation are higher in the male than in the female. 10. Sex-linked changes in glutathione peroxidase, in the rate of GSH oxidation and in the rate of lipid peroxide formation are discussed in relation to the metabolism of oestrogens in the liver and also to the possible nature of those sex-linked changes.     

Cytoplasmic oestradiol-binding sites and their relationship to oestradiol content in the endometrium of cattle.

Twenty-three cows and heifers were killed at known times during the oestrous cycle or during the first 35 days of pregnancy. Duplicate cytosol preparations were made from the endometrium of each uterine horn and both the binding-site concentration and the oestradiol level were determined for each sample. During the cycle, the oestradiol concentration was only 0-2 to 1-7% of the concentration of binding sites which varied considerably between Days 19 and 5 (47,665 +/- 7538 sites/cell, mean +/- S.E.M.) and Days 6 to 18 (7060 +/- 444 sites/cell). The concentration of binding sites remained low in pregnant animals (6689 +/- 492), although the oestradiol concentration was high about 20 days after insemination, resulting in almost 14% of the sites being occupied. Five inseminated animals in which no conceptus was found when they were slaughtered 19 to 22 days later had low concentrations of binding sites but two animals had high levels of oestradiol with 13% and 15%, respectively, of their cytoplasmic sites being occupied. It is suggested that these animals had recently lost their conceptuses. Two ovariectomized cows and one non-cyclic animal contained high concentrations of oestradiol-binding sites in the uterine cytoplasm. No significant difference was found between the uterine horn adjacent to the ovary with the CL and the contralateral horn in early pregnancy or during the luteal phase of the oestrous cycle. An animal killed 1 week after parturition contained fourfold more sites in the involuting horn than in the opposite horn. It is suggested that progesterone plays a major role in regulating oestrogen-induced replacement of cytoplasmic binding sites.     

Changes in neurohypophysial cholecystokinin content during oestrous cycle in the rat

Cholecystokinin content in the neurointermediate lobe of the rat pituitary was measured by radioimmunoassay during the different stages of the oestrous cycle. Higher levels were observed in pro-oestrus and oestrus than in metoestrus and dioestrus rats.

This difference is similar to the variation observed in the same circumstance concerning oxytocin in the neurohypophysis and neurosecretory activity in magnocellular neurons. These results are discussed in relation to the coexistence of oxytocin and cholecystokinin in neurons of the hypothalamoneurohypophysial system.     

Effects of progesterone and oestradiol on RNA and protein metabolism in the genital tract and on survival of embryos in the ovariectomized ewe.

The hormonal regulation of metabolism in the genital tract and the development of embryos during early pregnancy in the ewe have been examined. Ovariectomized ewes received injections of maintenance progesterone, oestrous oestradiol and priming progesterone according to schedules designed to simulate endogenous ovarian secretion during early pregnancy, around the time of oestrus and during the luteal phase of the oestrous cycle immediately preceding oestrus. The survival and development of embryos was dependent upon the dose of maintenaince progesterone and the duration of treatment at the time of transfer, but changes in progesterone dose did not change endometrial protein or RNA metabolism on particular days. Both priming progesterone and oestrous oestradiol were required for normal embryo development. Priming progesterone and oestrous oestradiol each increased endometrial RNA/DNA ratios during early pregnancy. There were no interactions between priming progesterone and oestrous oestradiol, their effects being simply additive. Neither maintenance nor priming progesterone had any effect on protein and RNA metabolism in the oviduct. It is suggested that in the intact ewe oestrogen secreted at oestrus and progesterone secreted prior to oestrus play important roles in the establishment of a uterine environment suitable for the subsequent normal development of embryos.     

Pregnancy, lactation and the oestrous cycle of the pouched mouse, Saccostomus campestris

The anatomy and histology of pouched mouse ovaries were studied during the oestrous cycle, pregnancy and lactation along with the relationship between the ovarian structures and circulating concentrations of progesterone. The structure of the ovaries resembled that of most rodents. Follicular development indicated that ovulation takes place on the night between pro-oestrus and oestrus, i.e. at the time when mating normally occurs. Corpora lutea were accumulating in cyclic females, while successively disappearing during pregnancy, leaving only the set formed after conception. After parturition luteal regression was rapid. Theca interna, included in the corpora lutea, formed glandular stromal tissue after regression of the luteal tissue formed from granulosa cells. The progesterone profile of non-pregnant females indicated a short but functional luteal phase (peak at metoestrus) during the cycle. During pregnancy three peaks of progesterone stood out: (1) when implantation starts, (2) when older sets of corpora lutea showed rejuvenation and placental signs were found in the vaginal smears, and (3) 3 days before expected parturition when luteal development (as judged by histology) reached a peak. The placenta may participate in but not 'take over' the progesterone production during later stages of pregnancy. Very low concentrations of peripheral progesterone during lactation and a very low level of follicular development at that time support an earlier suggestion of a lactational anoestrus in pouched mice.     

Influence of the oestrous cycle on L-glutamate and L-aspartate transport in rat brain synaptosomes.

Oestrous cycle and sex differences in sodium-dependent transport of L-[3H]glutamate and L-[3H]aspartate were investigated employing well washed synaptosomes prepared from rat brain cortex. Transport was best analysed on the basis of two components, a high and low affinity transport site. Oestrous cycle and sex differences were observed for both substrates. The high affinity transporter displayed highest affinity for glutamate transport in synaptosomes from female rats during proestrous and oestrous. This differed significantly from glutamate transport during dioestrous and in male rats. High affinity aspartate transport displayed highest affinity during oestrous and differed significantly from transport during dioestrous. Maximal velocity of high affinity glutamate transport was higher in synaptosomes from females during dioestrous compared with oestrous and lower in synaptosomes from male rats when compared with female rats in dioestrous and metoestrous. The low affinity sodium-dependent glutamate transporter displayed a 10-fold higher affinity for glutamate during proestrous than during the other three phases of oestrous and in male rats. Exogenously applied oestradiol and progesterone to synaptosomes from male rats showed no effect on glutamate or aspartate transport. No acute effect of oestradiol or progesterone on glutamate currents in oocytes expressing EAAT1 or EAAT2 subtype of glutamate transporter was observed. These results suggest hormonal regulation of high and low affinity sodium-dependent excitatory amino acid transporters over the four day oestrous cycle in synaptosomes from rat cortex. This regulation is unlikely to be due to a direct effect of oestradiol or progesterone on glutamate transporters.     

The effect of intrauterine and cervical manipulation on the equine oestrous cycle and hormone profiles.

Endometrial biopsy or endometrial biopsy and uterine culture taken on Day 4 after oestrus induced lysis of the corpus luteum (CL), resulting in a sharp decline in serum progesterone concentration and shortened the interoestrous interval in 8/12 and 32/33 oestrous cycles, respectively, during 2 experiments. Cervical dilatation 4 days after oestrus shortened the interoestrus interval in 5/10 and 0/5 oestrous cycles. Endometrial biopsy and culture on Days 1 and 3 after oestrus also induced CL lysis during 4 of 7 cycles. Total oestrogen (oestrone plus oestradiol) concentrations increased at the onset of the subsequent oestrus in mares biopsied on Day 4 of dioestrus or in control cycle oestrous periods. Endometrial biopsy also induced lysis of the CL in mares with persistent luteal function. It is postulated that intracervical or intrauterine manipulations during the luteal phase of the oestrous cycle may directly, or indirectly, stimulate the release of an endogenous luteolysin (prostaglandin) resulting in CL regression, followed by oestrus and ovulation in the mare.     

Expression and localisation of thioredoxin in mouse reproductive tissues during the oestrous cycle

Thioredoxin expression within the reproductive tissues of the female mouse was analysed during the oestrous cycle stages of dioestrus, oestrus and metoestrus by Western blot analyses and immunocytochemistry. From Western blot analyses the expression of thioredoxin was found to be increased in oestrus compared to dioestrus and metoestrus. Localisation of thioredoxin within the reproductive organs of the mouse during the oestrous cycle has shown that the expression of thioredoxin is specific for distinct areas within the reproductive organs. These areas are the stratified squamous epithelium of the vagina, the simple columnar epithelium and the uterine glands of the uterus, the ciliated columnar epithelium of the oviduct, the corpus lutea, the interstitial cells and the secondary follicles of the ovary. The discrete cellular localisation and oestrous dependence of thioredoxin expression are suggestive of specific roles in various reproductive processes.     

Effects of selenium toxicity on oestrous cyclicity, ovarian follicles, ovulation and foetal survival in rats

Effects of intraperitoneal injections of sodium selenite (2.0 and 4.0 mg/kg body weight) to normally cycling female albino Wistar rats daily for 30 days, and of single injection either during proestrous or oestrous and at each stage of the 4-day oestrous cycle were determined on oestrous cyclicity, ovarian follicles, ovulation, implantation and pregnancy outcome on day 14 of gestation. Administration of selenite for 30 days had no effect on the duration of first two oestrous cycles but afterwards the rats remained at the dioestrus stage. Their ovaries developed cystic follicles. Selenite treatments during the oestrous cycle preceding mating affects the implantation and pregnancy outcome in a dose-related manner. Its single dose containing 2.0 mg/kg body weight administered either at proestrous or oestrous, though had no effect on different reproductive parameters investigated in this study but its daily dose during the 4 day oestrous cycle reduced the number of corpora lutea and implantations as compared to saline injected control female rats. Similar effects of a single dose of selenite (4.0 mg/kg body weight) when injected at proestrous were recorded. Higher dose of selenite at oestrous or throughout the cycle decreased the number of implantations, but in addition, also increased the resorption rate/litter on day 14 of gestation. The present studies clearly show that high selenium levels in the body during the oestrous cycle preceding mating affects the number of ovulations, implantations and live embryos depending upon its dose and stage of administration.     

The acinar heterotopy of phosphoenolpyruvate carboxykinase activity in rat liver under the influence of the oestrous cycle

The acinar localization of phosphoenolpyruvate carboxykinase was investigated in livers from untreated female rats during the 4-day oestrous cycle. The results were correlated with plasma levels of insulin, glucagon and oestrogens. Total activity was highest in dioestrus and lowest in metoestrus. The highest activities were present in the periportal zone and decreased continuously towards the perivenous zone in all four phases of the cycle. This general pattern was modified under the influence of the cycle. The periportal-perivenous gradient was subject to cycle dependent changes, being steepest in proestrus. In addition to oestrogens the concentrations of plasma insulin also varied during the female cycle. Insulin was highest in oestrus and lowest in proestrus. Glucagon showed only minor variations. Oestrogen concentrations increased continuously from low values in oestrus to high values in proestrus. These changes were directly related to the changes in the slope of the activity gradient.     

Morphology and histochemistry of ovarian changes in the field rat, Millardia meltada

A study has been made of the morphological and histochemical changes of the ovary of the field rat, Millardia meltada during its oestrous cycle and pregnancy. The follicular growth and atresia, ovulation and formation of corpora lutea occur throughout the year except severe winter months (December and January). Fluctuations in the follicular development occur on different days of the oestrous cycle and pregnancy. The granulosa cells show a progressive increase in their size in successive stages of follicle growth. The granulosae of normal follicles show some sparsely scattered lipid bodies which consist of phospholipids. Theca interna cells during follicular growth develop diffuse lipoproteins and lipid droplets consisting of triglycerides, phospholipids and cholesterol and/or its esters. The luteal cells of corpora lutea are formed by the granulosa cells as the theca interna cells degenerate and disappear. The fibroblast-like cells of thecal origin, alongwith the blood vessels, invade the luteal cell mass. The luteal cells during metoestrus, dioestrus and first half of pregnancy show abundant diffuse lipoproteins and a few lipid droplets composed mainly of phospholipids and some triglycerides, which are indicative of active steroidogenesis. The details of degenerative histological and histochemical alterations of corpora lutea during oestrous cycle and pregnancy are also described and discussed. Morphological and histochemical changes of follicular atresia are described. The granulosa cells of atretic follicle degenerate and disappear leaving behind theca interna cells which form patches of interstitial gland cells during the reproductive activity of the present rat. Interstitial gland cells show diffusely distributed sudanophilic lipoproteins and lipid droplets consisting of triglycerides, cholesterol and/or its esters and some phospholipids, which are indicative of steroidogenesis. The functional significance of histological and histochemical changes, which occur in various components of the ovary during oestrous cycle and pregnancy, has been discussed.     

Micro-organisms and the appearance of leucocytes in the vaginal wall of cyclic female rats at metoestrus.

The present study was undertaken to examine whether leucocytic infiltration of the vagina of the rat at metoestrus is dependent on its contamination by micro-organisms. Observations were made on vaginal tissue that had been transplanted under the kidney capsule in cyclic rats, taking care to avoid infection during the transplantation procedure. In such grafts, changes occurred that were associated with ovulation and formation of the CL, but leucocytosis was never obtained at metoestrus. Cyclic changes were observed in the cell patterns of the vaginal smears of germ-free rats, and could be correled exactly with the ovarian cycle. No leucocytes were present at metoestrus. Many micro-orgainisms were present in the vagina at pro-oestrus and oestrus in normal cyclic females, but not at metoestrus and dioestrus. It is concluded that the occurrence of leucocytosis in the vagina at metoestrus in normal cyclic female rats depends on the presence of micro-oranisms.