Progesterone increases plasma volume independent of estradiol.

Adequate plasma volume (PV) and extracellular fluid (ECF) volume are essential for blood pressure and fluid regulation. We tested the hypotheses that combined progesterone (P(4))-estrogen (E(2)) administration would increase ECF volume with proportional increases in PV, but that P(4) would have little independent effect on either PV or ECF volume. We further hypothesized that this P(4)-E(2)-induced fluid expansion would be a function of renin-angiotensin-aldosterone system stimulation. We suppressed P(4) and E(2) with a gonadotropin-releasing hormone (GnRH) antagonist in eight women (25 +/- 2 yr) for 16 days; P(4) (200 mg/day) was added for days 5-16 (P(4)) and 17beta-estradiol (2 x 0.1 mg/day patches) for days 13-16 (P(4)-E(2)). On days 2 (GnRH antagonist), 9 (P(4)), and 16 (P(4)-E(2)), we estimated ECF and PV. To determine the rate of protein and thus water movement across the ECF, we also measured transcapillary escape rate of albumin. In P(4), P([P(4)]) increased from 2.5 +/- 1.3 to 12.0 +/- 2.8 ng/ml (P < 0.05) with no change in P([E(2)]) (21.5 +/- 9.4 to 8.6 +/- 2.0 pg/ml). In P(4)-E(2), plasma concentration of P(4) remained elevated (11.3 +/- 2.7 ng/ml) and plasma concentration of E(2) increased to 254.1 +/- 52.7 pg/ml (P < 0.05). PV increased during P(4) (46.6 +/- 2.5 ml/kg) and P(4)-E(2) (48.4 +/- 3.9 ml/kg) compared with GnRH antagonist (43.3 +/- 3.2 ml/kg; P < 0.05), as did ECF (206 +/- 19, 244 +/- 25, and 239 +/- 27 ml/kg for GnRH antagonist, P(4), and P(4)-E(2), respectively; P < 0.05). Transcapillary escape rate of albumin was lowest during P(4)-E(2) (5.8 +/- 1.3, 3.5 +/- 1.7, and 2.2 +/- 0.4%/h for GnRH antagonist, P(4), and P(4)-E(2), respectively; P < 0.05). Serum aldosterone increased during P(4) and P(4)-E(2) compared with GnRH antagonist (79 +/- 17, 127 +/- 13, and 171 +/- 25 pg/ml for GnRH antagonist, P(4), and P(4)-E(2), respectively; P < 0.05), but plasma renin activity and plasma concentration of ANG II were only increased by P(4)-E(2). This study is the first to isolate P(4) effects on ECF; however, the mechanisms for the ECF and PV expansion have not been clearly defined.     

Progesterone and estradiol in biodegradable microspheres for control of estrus and ovulation in mares

Progesterone and estradiol 17-beta in poly (DL-lactide) microspheres were used to control estrus and ovulation in mares after luteolysis was induced by prostaglandin F(2)infinity. Mares were given a single intramuscular injection of biodegradable poly (DL-lactide) microspheres, 1 day following prostaglandin treatment, containing no hormones (control), 0.625 g progesterone and 50 mg estradiol (low dose), 1.25 g progesterone and 100 mg estradiol (medium dose), or 1.875 g progesterone and 150 mg estradiol (high dose; n=15 mares per group). Mares treated with the low dose had significantly longer intervals (P<0.05) to estrus and ovulation than the control mares; however, low dose mares had shorter intervals (P<0.05) to estrus than high dose mares and shorter intervals to ovulation than medium and high dose mares. Regression analysis indicated that the medium dose was sufficient for maximizing interval to ovulation while the high dose maximized interval to estrus. All groups of mares exhibited similar (P>0.05) post-treatment estrus lengths. A clinical response scoring system based on synchrony of both estrus and ovulation within a treatment group was also used to measure the effectiveness of treatments on control of estrus and ovulation. Clinical response scores did not differ (P>0.05) among treatment groups. Mares were randomly assigned for insemination at the beginning of the first post-treatment estrus. Rates for embryo recovery performed by uterine lavage 7 days post-ovulation did not differ (P>0.05) among groups. Concentrations of serum progesterone increased in mares receiving progesterone and estradiol microspheres. At 10 to 14 days post-injection of microspheres, progesterone concentrations were higher (P<0.05) and remained above 1 ng/ml in the mares receiving the high dose. Progesterone concentrations were also higher (P<0.05) on Days -3 to -1 (Day 0 = day of post-treatment ovulation) in mares receiving the high dose when compared to control mares. Gonadotropin concentrations were suppressed (P<0.05) in the medium and high dose groups.     

Progesterone facilitation of lordosis in male and female Sprague-Dawley rats following priming with estradiol pulses

Adult male Sprague-Dawley rats rarely exhibit progesterone-facilitated lordosis following steroid treatments which are effective in females. In contrast, progesterone-facilitated lordosis has been observed following priming with estradiol pulses in another strain. The aim of this study was to compare progesterone-facilitated feminine sexual behavior in adult male and female Sprague-Dawley rats following priming with estradiol benzoate (EB) or estradiol pulses. Female sexual behavior was measured in adult, gonadectomized males and females treated as follows: Two pulses of estradiol followed by progesterone or oil the next day; EB (two doses) for 3 days, and progesterone or oil the next day. These protocols were repeated at 4- or 6-day intervals, respectively. Progesterone-facilitated lordosis was observed consistently in both sexes treated with estradiol pulses. By the fifth test, lordosis quotients did not differ between the sexes, but the lordosis ratings in progesterone-treated males remained lower than those observed in females. Proceptivity (hop-darting) was facilitated by progesterone in females, but was never observed in males. Lordosis was induced in both sexes by 15 micrograms EB, but was not reliably facilitated by progesterone. Treatment with the lower dose of EB (1.5 micrograms) induced high levels of receptivity in females (occasionally facilitated by progesterone), but not in males regardless of subsequent treatment (i.e, progesterone or oil). These data suggest that progesterone-facilitated lordosis can be induced in male Sprague-Dawley rats, if a regimen of estradiol pulses is used. Thus, the brain of the adult male is not inflexibly differentiated with regard to progesterone facilitation of feminine receptive behavior.     

Partial purification of estradiol receptor from Xenopus laevis liver and levels of receptor in relation to estradiol concentration

We have used ammonium sulphate precipitation followed by affinity chromatography to partially purify the estrogen receptor from Xenopus laevis liver which may control the genes for vitellogenin, the precursor of the egg yolk proteins. The rate at which receptor binds estradiol explains the kinetics of the induction of vitellogenin synthesis by estradiol, and the dissociation constant (0.5 X 10(-9) M) explains the concentration dependence of the response, which has a threshold of 10(-9) M estradiol, when 67% of the receptor is bound to estradiol. The estradiol concentration in male liver, which does not make vitellogenin, is 0.18 X 10(-9) M, sufficient to saturate 26% of the receptor, while in female liver, which makes vitellogenin continuously, the estradiol concentration is 3.5 X 10(-9) M, giving 88% saturation of receptor, suggesting that the proportion of occupied receptor decides whether or not the vitellogenin genes are active. In the physiological concentration range, estradiol modulates the level of receptor, which varies between 100 binding sites per nucleus in males and 440 in females, but artificially high concentrations of estradiol raise the level to approximately 1000 sites per nucleus. This suggests that the small increase in vitellogenin mRNA induced by physiological concentrations of estradiol is due to pre-existing receptor and that the much larger increases induced by very high concentrations depends on newly-synthesized receptor.     

Social regulation of plasma estradiol concentration in a female anuran

The behavior of an individual within a social aggregation profoundly influences behavior and physiology of other animals within the aggregation in such a way that these social interactions can enhance reproductive success, survival and fitness. This phenomenon is particularly important during the breeding season when males and female must synchronize their reproductive efforts. We examined whether exposure to conspecific social cues can elevate sex steroid levels, specifically estradiol and androgens, in female túngara frogs (Physalaemus pustulosus). We compared plasma estradiol and androgen concentrations in wild-caught females before and after exposure to either natural mate choruses or random tones. After exposure to mate choruses for 10 consecutive nights, estradiol concentrations were significantly elevated whereas there was no significant elevation in estradiol concentrations in the group of females exposed to random tones for 10 nights. Plasma androgen concentrations were not significantly changed after exposure to either natural mate choruses or random tones for 10 consecutive nights. Social modulation of estradiol concentrations may be important in maintaining a female's reproductive state while males are chorusing. To our knowledge, this is the first study to demonstrate social regulation of estradiol concentration in female anurans.     

The endogenous concentration of estradiol and estrone in pathological human postmenopausal endometrium

The endogenous estrone (E1) and estradiol (E2) levels (in pg/g tissue) were measured in 7 postmenopausal patients with a hyperplastic endometrium, in 3 with an atypical adenomatous hyperplastic endometrium and in 13 with a carcinomatous endometrium. These tissue concentrations were compared with the E1 and E2 concentrations in plasma (pg/ml) and with data from a control group of postmenopausal women with atrophic endometria. The tissue levels of both steroids showed large variations and there were no significant correlations with their plasma levels. In the hyperplastic and the atypical adenomatous hyperplastic group the mean E2 tissue level was higher compared with the mean E1 tissue level, despite the excess of E1 over E2 in peripheral plasma. In the carcinomatous group the mean E1 tissue level was higher, although not significantly, than the mean E2 tissue level. There were no significant differences between the E1 and E2 tissue levels in the three different pathological groups as compared to the atrophic control group. We conclude that it is unlikely that estrogens alone play a crucial role in the development of a pathological endometrium.     

Progesterone and follicular changes in postpartum noncyclic dairy cows after treatment with progesterone and estradiol or with progesterone, GnRH, PGF2alpha, and estradiol

A previous study showed that noncyclic dairy cows treated with 10 microg of GnRH and a progesterone-releasing CIDR insert on Day 0, 25 mg of PGF2alpha and CIDR removal on Day 7, followed by 1 mg estradiol benzoate on Day 9 for those cows that still had not shown estrus (CGPE program) had higher conception rate (47% vs. 29%) than cows treated only with CIDR and estradiol benzoate as above (CE program). This study was to investigate the mechanisms by which the CGPE program improved conception rate compared with the CE program. Sixteen noncyclic Holstein-Friesian cows were randomly assigned to 2 groups balanced for the size and growth pattern of the dominant follicles, which were determined by ultrasonography over a 3-d period. One group received the above CGPE treatment, and the other group received the CE treatment. Follicular and luteal development were monitored by daily ultrasonography. Blood samples were collected daily from Day -2 to Day 11, and thereafter milk samples were collected thrice weekly for a further 24 d. Blood and milk samples were analyzed for progesterone. The GnRH treatment induced ovulation in 7 of 8 cows, resulting in elevated (P<0.05) progesterone concentrations between Days 4 and 7 for cows in the CGPE group. All induced CL underwent luteolysis by 24 h after PGF2alpha treatment. Within 5 d of CIDR removal, 7 of 8 cows in both the CE and CGPE groups ovulated. The interval from emergence of the ovulatory follicle to ovulation was similar (P=0.32) but less (P<0.05) variable for the CGPE group (9.0+/-0.3 d) compared with the CE group (10.3+/-1.2 d). Progesterone concentration in milk samples was similar between the two groups up to 10 d after ovulation. In summary, the GnRH treatment induced ovulation or turnover of dominant follicles, induced a synchronized initiation of a new follicular wave, and increased the progesterone concentration from 4 d after treatment. These could be the reasons for the increased conception rate of cows treated with the CGPE program.     

Regulation of estradiol and progesterone receptor concentrations in cat uteri following chronic progesterone administration

The purpose of this study was to determine the early effect of progesterone (P) on the estradiol (E2) and P receptor systems in cat uteri. Ovariectomized animals were treated with E2 for 7 days. Animals were then treated for up to 48 h with E2 and P, treated with P while being E2 withdrawn, or just E2 withdrawn. P treatment resulted in a significant decrease in P cytosol receptor (PcR) and a significant increase in P nuclear receptor (PnR) at all times included in this study when compared to levels measured in the E2-treated animal. E2 cytosol receptor (EcR) and E2 nuclear receptor (EnR) levels were significantly lower after 12 h of P treatment and remained so for the duration of this study. When EcR and EnR levels were compared after 48 h of P treatment in the presence or absence of E2, or after 48 h of E2 withdrawal, the loss of EnR following P treatment appeared to be independent of any changes in EcR levels or serum E2 levels, and only dependent on the presence of P. These results clearly illustrate that the chronic administration of P decreases the uterine concentration of its own receptor, and suggests that P decreases the E2 receptor system by a selective action within the nucleus which diminishes their ability to retain EnR.     

Progesterone synthesis by pig corpus luteum tissue during superfusion

A modified superfusion technique is described with which it was demonstrated that the action of gonadotrophin on progesterone secretion by pig corpus luteum tissue is twofold, in that it first stimulates the rapid release of progesterone (either performed or partially synthesized), which is followed by prolonged synthesis of the steroid de novo from acetate.     

Progesterone concentration and reproduction: An evaluation in pregnant, heat-acclimated, white rats

1. 1.|Progresterone concentrations in peripheral plasma, corpus luteum, uterus and placenta were determined by radioimmunoassay, in pregnant heat-acclimated (HA) and control (C) rats.

2. 2.|Concentration of progesterone in plasma and uterus of HA rats were lower than C from day 5 to 18 and day 5 to mid-gestation respectively.

3. 3.|Number and weight of pups born to HA rats were lower than C by 11.1% and 12.3% respectively.

4. 4.|It is concluded that aberration in pregnancy development observed in HA rats is associated with lower progesterone concentration in plasma and uterus from day of implantation to mid-pregnancy.

Progesterone and RU486 regulation of uterine complement C3 after prior induction with estradiol.

Previous results demonstrated that progesterone (P4) given simultaneously with estradiol (E2) prevented stimulation by E2 of complement C3 expression in the immature rat uterus. Northern blot analysis revealed that simultaneous administration of P4 was able to prevent the E2-stimulated increase in C3 mRNA concentration in the luminal epithelial cells. The purpose of the present investigation was to determine whether progesterone modulates C3 expression after the gene has been induced by prior administration of E2 and also to determine the reversibility of this effect by the concomitant administration of RU38486, 17 beta-hydroxy-11 beta-[4-dimethylaminophenyl]estra-4,9,-dien-3-one (RU486). This regulation was studied by examination of protein synthesis as well as mRNA concentrations. Immature 21-day-old female rats were treated with E2 for 2 days (1 microgram/day), followed 24 h later by P4 (500 micrograms) or vehicle. Uteri were removed 6, 9, and 18 h after progesterone treatment and the radiolabeled secreted proteins were analyzed by SDS-PAGE and immunoprecipitation using a goat anti-rat C3 antibody. In animals treated with vehicle, E2-stimulated C3 synthesis remained elevated at 6 and 9 h and returned to control values by 18 h. In contrast, the administration of P4 resulted in a decrease in C3 synthesis at 6 and 9 h with the greatest decrease observed at 9 h. Similar results were obtained when C3 mRNA concentrations were examined. E2-stimulated C3 mRNA concentrations were decreased in rats treated with progesterone compared to those treated with vehicle alone.2     

Progesterone in uterine and arterial tissue and in jugular and uterine venous plasma of sheep

Concentrations of progesterone in uterine and arterial tissue and in uterine and jugular venous plasma were determined. Blood was collected on Days 4 and 9 postestrus from the jugular vein and the first and last venous branches draining each uterine cornu; uterine tissue and arteries were subsequently collected. Progesterone was greater (p less than 0.05) in the cranial third than in the middle or caudal thirds of the uterine horn adjacent to the corpus luteum (CL)-bearing ovary or in any third of the contralateral horn. Progesterone in uterine arterial segments adjacent to the CL-bearing ovary was higher (p less than 0.05) than in contralateral segments. Progesterone was higher (p less than 0.05) in blood from the first venous branch of the cranial third of the uterine cornu adjacent to the ovary with the CL, than in the last branch of the caudal third, or contralateral horn, or in jugular blood. When oviductal veins were resected on Day 9 postestrus, progesterone in the first vein draining the cranial third of the uterine cornu adjacent to the CL-containing ovary was not different (p greater than 0.05) 48 h after resection than in the same vessel in the opposite horn or in jugular blood. We concluded that progesterone and other ovarian products may be delivered to the uterus locally.     

Interrelationship between plasma estradiol concentration and oxytocin-induced PGF2alpha release in heifers

The objective of this study was to determine if the increase in responsiveness to oxytocin toward the time of luteolysis was correlated with an increase in plasma estradiol in the cow. Six heifers each had a cannula placed in the jugular vein on Day 14 of the estrous cycle. Then, beginning on Day 15, growth of the largest follicles was determined by ultrasonography, and a blood sample was taken via the cannula for the measurement of progesterone and estradiol by radioimmunoassay (RIA). After the first blood sample, 3 more samples were taken at 10-min intervals, 100 IU oxytocin were injected into the vein, and a further 3 blood samples were taken at 15, 30 and 60 min after injection. The concentration of 13,14-dihydro-15-keto prostaglandin F2alpha (PGFM) was measured in these frequent samplings and was used to determine the ability of oxytocin to stimulate PGF2alpha release from the uterus. This procedure was repeated daily for at least 7 d. The results showed that the response to oxytocin increased before luteolysis and that there was a significant increase in the response to oxytocin (P<0.05) before any changes in plasma estradiol or progesterone were detected. These data show that an increase in estradiol secretion from the ovulatory follicle does not appear to initiate luteolysis.     

The effect of estradiol and progesterone application on leptin concentration in ovariectomized rats

The aim of the present study was to investigate the effects of estradiol and progesterone application on leptin secretion in ovariectomised rats. The study included 30 adult female Sprague-Dawley rats. Rats were divided into three groups as follows: Group 1; Sham ovariectomy group (n=10), Group 2; Ovariectomy group (n=10), Group 3; Ovariectomized and estradiol propionate (450 microg/kg rat) and medroxyprogesterone acetate (15 mg/kg rat) supplemented group (n=10). One week after ovariectomy, rats in Group 3 were injected estradiol and progesterone for 4 weeks. Twenty-four hours after the last injection, rats were decapitated and blood samples were collected for leptin analysis. Serum leptin levels in Group 2 were found significantly higher than those in Groups 1 and 3 (p<0.01), while those in Group 3 were significantly lower when compared to Group 1 (p<0.0 1). The findings of the present study have shown that ovariectomy led to a significant increase in leptin levels. However, administration of estradiol and progesterone in combination following ovariectomy inhibites increases of leptin levels.     

Plasma estradiol FSH and LH concentration after dominant follicle aspiration in the cow

This work investigates the estrogenic role of the dominant follicle with regard to regulation of plasma FSH and LH concentration. Eight Holstein-Friesian cows were used for aspiration of the dominant follicle using ultrasound guidance during the early, mid and late stages of the luteal phase. Blood samples were collected at 15-min intervals from 4 h before until 7 h after aspiration. Plasma progesterone concentration increased from 0.7 to 7.2 ng mL-1 from early to mid luteal phase and then fell slightly to 5.9 ng mL-1 in the late luteal phase, but remained unaffected by follicle puncture. The follicular aspirate contained a thousandfold higher estradiol, than plasma concentration but its estradiol:progesterone ratio remained at around 2 at each stage of the luteal phase. Aspiration caused plasma estradiol concentration to fall from 1.4 to 0.7, 1.8 to 1.0 and 1.7 to 0.8 pg mL-1 in the early, mid and late stages of the luteal phase, respectively (P < 0.05). At the same time, mean plasma FSH concentration was increased from 1.1 to 1.8, 1.7 to 2.9 and 0.8 to 1.9 ng mL-1 (P < 0.05), respectively. The results suggest that estradiol secreted from dominant follicles selectively regulates gonadotropin secretion, since aspiration of the dominant follicle at any stage of the cycle affected circulating FSH but did not appear to influence the mean LH concentration.