Differential effect of the 17β-aminoestrogens prolame, butolame and pentolame in anxiety and depression models in rats

Estrogens of clinical use produce consistent antidepressant- and anxiolytic-like effects in animal models of menopause. Regulation of the hypothalamic-pituitary-adrenal (HPA) or stress axis, has been proposed as a pathway through which estrogens improve affective-like behaviors. Anticoagulant 17β-aminoestrogens (17β-AEs) butolame and pentolame mimic some effects of estradiol (E2), i.e., on female rodent sexual behavior, with opposite actions on coagulation. However, their psychoactive actions have not been explored. On the basis of similitude with E2's effects, we hypothesized that these 17β-AEs would induce anxiolytic- and antidepressant-like effects, which would be reflected in a reduction of activity in the HPA axis. In ovariectomized female rats, chronic treatment with prolame (60 μg/kg), butolame (65 μg/kg) and pentolame (70 μg/kg) reduced anxiety-like behavior in the elevated plus maze (evidenced by an increase in time in open arms, E2 (40 μg/kg) +176%; prolame +201%; butolame, +237%; and pentolame +295%, in comparison to the control vehicle group 100%). Pentolame also decreased significantly anxiety-like behavior in the burying behavior test. Prolame and E2 produced a significantly antidepressant-like action, which was not induced by butolame and pentolame. Behavioral effects of 17β-AEs (and E2) on anxiety and depression did not follow the same pattern than corticosterone or E2 levels; they also were associated to changes in locomotor activity, evaluated by the open field test. These results constitute the first evidence of specific and selective actions of butolame and pentolame as anxiolytics for females with a hypoestrogenic condition. Results also confirm the potential of prolame as an antidepressant steroid with equivalent actions to E2. Psychoactive properties of 17β-AEs in combinations with reduced adverse effects on coagulation, suggest that 17β-AEs may be a good alternative replacement therapy for women with symptoms associated with menopause.

Estrogen and tibolone metabolite levels in blood and breast tissue of postmenopausal women recently diagnosed with early-stage breast cancer and treated with tibolone or placebo for 14 days

Unlike estrogens plus progestagens, tibolone, a selective tissue estrogenic activity regulator, does not increase breast tenderness and mammographic density. To elucidate this, serum and breast levels of tibolone and estrogenic metabolites are measured. Postmenopausal women (n = 102) with early-stage, ER(+ve), primary breast cancer received tibolone or placebo for 14 days in an exploratory, double-blind, randomized trial (STEM carcinoma tissue). Baseline and presurgery sera were collected; tumor tissues were obtained at surgery. E(1) (estrone), E(2) (estradiol), E(1)S (estrone-sulfate), tibolone-its nonsulfated, monosulfated, and disulfated 3-hydroxymetabolites-and Delta(4)-tibolone were measured by validated gas chromatography and mass spectrometry and liquid chromatography with tandem mass spectrometry assays. More than 12 hours after the final dose, serum E(1), E(2), and E(1)S levels were unchanged with placebo, whereas tibolone significantly increased E(1)S and the E(1)S/(E(1) + E(2)) ratio. In tumors, E(1) and E(2) levels were higher than in serum, and E(1)S levels were lower, with placebo and tibolone administration. The percentage of E(1)S was about 90% in serum and 16% in tissue. Tibolone did not affect tissue levels of endogenous estrogens. Serum levels of estrogenic 3alpha- and 3beta-hydroxytibolone, progestagenic/androgenic Delta(4)-tibolone, and monosulfate metabolites were low. Serum 3alphaS,17betaS-tibolone and 3 betaS,17betaS-tibolone levels were 250 and 52 ng/mL, respectively. Tumor levels of 3alpha- and 3beta-hydroxytibolone and Delta(4)-tibolone were higher than in serum, but disulfate levels were lower. The percentage of sulfated tibolone metabolites was 99% in serum and 96% in tumor. Serum metabolite patterns of estradiol and tibolone are different from those in tissues and are compatible with neutral effects of tibolone on breast Ki67 expression.

Intrauterine release of progesterone antagonist ZK230211 is feasible and results in novel endometrial effects: a pilot study

BACKGROUND

Continuous administration of progesterone antagonists (PAs) results in endometrial suppression and amenorrhoea in several model systems. We compared the effects of intrauterine release of a highly specific PA, ZK230211, to those of a progestin using the levonorgestrel-releasing intrauterine system (LNG-IUS).

METHODS

Forty-two women were randomly fitted with an IUS releasing either ZK230211 at a rate 1, 4 or 8 microg/24 h (ZK-IUS) or LNG (at 20 microg/24 h, LNG-IUS) at 4-8 weeks before hysterectomy. Bleeding patterns, endometrial morphology and content of ZK230211, and various immunohistochemistries (IHCs) were evaluated.

RESULTS

Days of bleeding and spotting were unchanged by the use of ZK-IUSs but were increased by LNG-IUS (P < 0.01). ZK230211 was measurable in all endometrial specimens. Endometrium was partly suppressed in 9-30% of women following the use of ZK-IUSs, and in 67% after LNG-IUS. IHCs for Ki-67 and phosphorylated histone H3 were not suggestive of proliferative activity in any group. Compared to LNG, progesterone receptor (PR) was increased following ZK230211 in surface epithelium (all three doses P < 0.01-P < 0.05) and stroma at 4 microg/24 h (P < 0.05). Although low, androgen receptor staining was higher in endothelial epithelium following LNG than ZK230211 (P < 0.05). Insulin-like growth factor-binding protein-1 (IGFBP-1) was detectable only following LNG (P < 0.0001).

CONCLUSIONS

Short-term intrauterine release of ZK230211 did not change bleeding patterns or result in endometrial suppression. Expression of proliferation markers was low following the use of both IUSs. Absence of IGFBP-1 and increase in PR reflect the PA effects of ZK230211.

Biowaivers for oral immediate-release products: implications of linear pharmacokinetics

Bioequivalence of drug formulations plays an important role in drug development. Recently, the Biopharmaceutical Classification System (BCS) has been implemented for the purpose of waiving bioequivalence studies on the basis of the solubility and gastrointestinal permeability of drug substance. Using the rationale of the BCS, it can be argued that biowaivers can, however, also be granted on the basis of standard pharmacokinetic data. If a drug exhibits dose-linear pharmacokinetics and a sufficiently fast dissolution profile, it can be concluded that this drug appears to pose no problem with respect to absorption. It should be noted that a change of an immediate-release tablet formulation can only lead to a deviating rate and/or extent of absorption when release of the drug from the formulation is altered. Logically, the dissolution profiles of the different formulations should be equal to guarantee bioequivalency. Thus, both BCS and the alternative linear pharmacokinetics approach require an evaluation of dissolution profiles. The justification of BCS is found in the permeability classification of the compound, while those of the linear pharmacokinetics lie in the apparent lack of a permeability problem. For example, in this context P-glycoprotein-transported drugs form an interesting class of compounds, which may be treated likewise when complying to the aforementioned requirements. Furthermore, poorly soluble compounds may be less troublesome than expected. It is shown that linear kinetics can be explained by the solubilising activity of, for example, bile salts. In this instance, linear pharmacokinetics shows that elevated doses do not appear to exhibit a limiting role on the dissolution. Hence, a change in formulation without any effect on the dissolution profile is not expected to cause a change in availability. It is clear that the formulations to be compared should not contain excipients that display an effect on (presystemic) drug metabolism.

Pharmacokinetics of 7 alpha-methyl-19-nortestosterone (MENT) delivery using subdermal implants in healthy men

We studied the pharmacokinetics of 7 alpha-methyl-19-nortestosterone (MENT), a potent synthetic androgen, administered by subdermal implants. The implants contained 112 +/- 4 mg of MENT acetate in a polyethylene vinyl acetate copolymer. MENT acetate released from the implants is rapidly hydrolyzed to MENT in vivo. Fifteen healthy Finnish men were randomized to have either one, two, or four implants inserted in the medial aspect of the upper arm. The implants remained in place for 4 weeks. Blood samples were obtained before implant insertion, 1, 2, 3, and 4 weeks after insertion, and 1 and 2 weeks after removal. Serum MENT concentrations were determined by gas chromatography with mass selective detection. The MENT levels attained in each implant group remained at a steady level during the 4 weeks of implant use. The mean steady state MENT concentrations in the one, two, and four implant groups were 0.6, 1.4, and 2.3 nmol/L, respectively. Serum MENT concentrations during implant use were clearly dose dependent; the between-subject effect of implants as well as the differences between each pair of groups were all statistically significant. The release rate of MENT from one, two, and four implants was calculated to be approximately 0.3, 0.8, and 1.3 mg/day, respectively. This study suggests that MENT acetate implants are a promising method for long-term androgen administration in hypogonadism and male contraception.

Measurement of steroid hormones in plasma by isocratic high performance liquid chromatography coupled to radioimmunoassay

The study of steroidal profiles requires simultaneous determinations of various steroid hormones that cannot be appropriately carried out with the conventional routine immunoassays. Moreover, there are several trials for which the assessment of multiple steroids from a single serum sample is mandatory. In this paper we describe a procedure for simultaneously measuring steroid hormones using a unified solid phase extraction which allows the measurement of both unconjugated and conjugated steroids from 1 ml of sample and a combination of HPLC with isocratic elution followed by RIA. The entire procedure was preliminary carried out for the measurement of testosterone, dehydroepiandrosterone and its sulphated conjugate, androstenedione and 17 hydroxyprogesterone. The use of this technique allows precise and accurate measurements of steroid profile with a single serum aliquot and could be helpful in the diagnosis of various form of endocrine disorders.

Antiarrhythmic, electrophysiological and haemodynamic effects of prolonged oral dosing with Org 7797 in the anaesthetized rat

The antiarrhythmic, electrophysiological and haemodynamic effects of chronic oral administration of Org 7797 ((16 alpha,17 beta)-17-methylamino-oestra-1,3,5(10)-triene-3, 16-diol-(Z)-2-butonedioate) were studied in rats. During dosing (10 mg kg-1 twice a day for 10 days) no effects on the electrocardiogram, monitored in conscious animals, were observed despite modest reductions (15-18%) in the maximum rate of depolarization of papillary muscle excised 1 or 6 h after completion of the dosing regime. Following anaesthesia, Org 7797 reduced the severity of arrhythmias induced by coronary artery occlusion and prevented the accompanying decrease in the ventricular fibrillation threshold (VFT) at 1 h after completion of dosing. By 6 h the effect on VFT had waned but protection against ischaemia-induced arrhythmias was retained despite a substantial decrease in Org 7797 plasma levels. Drug treatment did not modify arterial blood pressure, heart rate or stroke volume. We conclude that Org 7797 given chronically via the oral route exerts antiarrhythmic actions which may, at least in part, be due to sodium-channel block. In addition, our results suggest the presence of an active metabolite. The protective effects of Org 7797 were seen in the absence of electrocardiographic or haemodynamic changes suggesting that multiple oral doses of Org 7797 do not compromise normal cardiac function.

Radioimmunoassay of 7 alpha-methyl-19-nortestosterone and investigation of its pharmacokinetics in animals

A method for the measurement of 7 alpha-methyl-19-nortestosterone (7MENT) in serum/plasma by radioimmunoassay (RIA) is described. The antiserum, raised against 7 alpha-methyl-19-nortestosterone-3-O-oxime-bovine serum albumin, had a low titer (final dilution = 1:4500) and low affinity (Ka = 1.17 x 10(9) l/mol) but showed little or no cross-reactivity with several of the steroids tested. The sensitivity of the RIA was 28.2 pg/ml and the mean recovery of added cold steroid was 86 to 100%. Intra- and inter-assay coefficients of variation ranged from 4.3 to 7.3% and 7.3 to 8.4%, respectively. This RIA was used to follow plasma 7MENT levels after a single i.v. injection of the steroid in rats and rabbits. The metabolic clearance rates (MCR) of 7MENT as determined from the plasma disappearance curve for rats and rabbits were 50 l/day and 336 l/day, respectively. The MCR of 7MENT in rats and rabbits lies in the same range as for testosterone. When compared to other nortestosterone derivatives such as norethisterone, 7MENT is metabolized relatively faster.

Levels of the antiprogestin RU 486 and its metabolites in human blood and follicular fluid following oral administration of a single dose

Using high-pressure liquid chromatography (HPLC) the antiprogestin RU 486 and two of its metabolites (N-monodemethyl RU 486 and propargyl RU 486) were measured in plasma and follicular fluid of 21 women requesting laparoscopic sterilization. Pretreatment of the women involved ovulation induction with clomiphene and HCG. RU 486 (100 mg) was administered orally and 1 h later blood samples were withdrawn. Thirty-four hours later, at laparoscopy, samples of both blood and follicular fluid were collected. During the 34-h period the average plasma level of RU 486 decreased from 1.93 mumol/l to 0.91 mumol/l, i.e. by -50%. The latter concentration of RU 486 was not significantly different from that found in follicular fluid (0.79 mumol/l). The monodemethyl metabolite exhibited significantly higher plasma levels (3.09 mumol/l) than RU 486 1 h after administration. Thirty-four hours later these levels had decreased to 0.92 mumol/l, i.e. by 70%. In follicular fluid, the levels of the monodemethyl metabolite (1.76 mumol/l) were significantly higher than those of RU 486 (0.79 mumol/l). Because of background noise, only approximate values were established for the propargyl metabolite. These were 0.67 and 0.40 mumol/l, respectively, in plasma and 0.42 mumol/l in follicular fluid. The results indicate that RU 486 and two of its major metabolites can readily cross the blood-follicle barrier of human pre-ovulatory follicles.

Distribution of RU 486 and its demethylated metabolites in humans

The concentrations of RU 486 and its demethylated metabolites were determined by RIA in samples of myometrium, abdominal adipose tissue, and serum, which were collected at hysterectomies performed 12-15 h after oral administration of 200 mg RU 486. The RU 486 concentrations in myometrium were similar in the five women studied, with a mean of 148 +/- 58 (+/- SD) ng/g (344 +/- 135 pmol/g). The adipose tissue RU 486 levels varied more, the mean concentration being 447 +/- 191 ng/g (1041 +/- 445 pmol/g). The serum RU 486 concentrations ranged from 175-899 ng/ml [mean, 396 +/- 259 ng/mL (922 +/- 603 nmol/L)]. In these women the nonprotein-bound fraction of [6,7-3H]RU 486 varied from 1.4-3.1% (mean, 2.3%). The approximate concentrations of the combined mono- and didemethylated metabolites of RU 486 were 1.4, 3.1, and 5.2 times higher in adipose tissue, myometrial tissue, and serum, respectively, than those of the parent RU 486. In vitro, rapid and nonsaturable accumulation of [6,7-3H]RU 486 from phosphate buffer into adipose tissue was inhibited by the addition of alpha 1-acid glycoprotein, the specific serum transport protein for RU 486, to the buffer medium. Accumulation of [6,7-3H]RU 486 in myometrial specimens was poor. The enterohepatic cycling of RU 486 was assessed in four normal subjects by repetitive intake of charcoal subsequent to ingestion of 200 mg RU 486. Compared to other normal subjects, the serum levels and areas under the concentration curves were lower and t1/2 values shorter in the group given charcoal, suggesting that in vivo RU 486 may be partly pooled in the enterohepatic cycle. Our studies suggest that despite the low volume of distribution and the effective serum binding of RU 486, the myometrial and adipose tissue concentrations of RU 486 and its metabolites were similar (approximately 10(-9)-10(-10) mol/g) after oral intake of RU 486.

Pharmacokinetics of the antiprogesterone RU 486 in women during multiple dose administration

Serum levels of RU 486 were measured by high performance liquid chromatography (HPLC) following oral intake of 12.5, 25, 50 and 100 mg twice daily (b.i.d.) for 4 days, 50 mg b.i.d. for 7 days, as well as a single dose of 200 mg of RU 486. The pharmacokinetics of RU 486 were not linear: when the daily dose of RU 486 was 100 mg or more, the serum levels were similar. The pharmacokinetic behaviour of RU 486 during the treatment period was similar between the study subjects, whereas the elimination phase pharmacokinetics showed wide individual variation. Also the mean elimination phase half-lifes (t 12) of RU 486 varied from 25.5 to 47.8 h in the groups of different regimen, yet the variation between different groups was not statistically significant. The areas under the concentration curves (AUC) were calculated. In the multiple dose study (mds) the AUC0----12h:s decreased when the administered dose of RU 486 was increased. The AUC0----12h seen after administration of 100 mg b.i.d. x 4d. (mean +/- SEM = 0.43 +/- 0.04 mumol/l x h/mg) was significantly (P less than 0.05) lower than the AUC0----12h:s obtained with administration of 12.5 mg b.i.d. x 4d. (1.49 +/- 0.37 mumol/l x h/mg), 25 mg b.i.d. x 4d. (1.09 +/- 0.15 mumol/l x h/mg), and 50 mg b.i.d. x 7d. (0.72 +/- 0.11 mumol/l x h/mg). The AUC0----infinity obtained by administration of a single dose of 200 mg of RU 486 (sds) was 0.67 +/- 0.21 mumol/l x h/mg. It is concluded that if multiple dose administration of RU 486 is preferred, daily administration of relatively small doses of RU 486 over several days seem to be advantageous.

Inhibition of folliculogenesis and ovulation by the antiprogesterone RU 486

Healthy, regularly menstruating women were treated with the antiprogesterone RU 486, Mifepristone (Roussel-Uclaf, Romainville, France) during the follicular phase of the cycle. Three women were given 25 mg of RU 486 on days 1 to 14 of the cycle and five received 25 mg on days 1 to 21 of the cycle. Venous blood samples were collected three times per week during a control cycle and during one treatment cycle in each subject. Serum concentrations of estradiol (E2), progesterone (P), and RU 486 were determined by radioimmunoassays. No drug-related side effects and no spotting or bleeding during RU 486 treatment were observed. Menstrual bleeding was delayed by 8.7 +/- 3.8 days (mean +/- SD) after treatment over days 1 to 14 and by 12.6 +/- 3.2 days after treatment over days 1 to 21. During the treatment with RU 486, the serum concentrations of E2 remained low, indicating effective inhibition of folliculogenesis. After cessation of RU 486 treatment, serum E2 levels rose to similar values as in the control cycle, and subsequently serum P concentrations also reached ovulatory levels in six out of the eight volunteers. The results showed that the antiprogesterone RU 486 delayed folliculogenesis and luteinization even at low doses when given during the follicular phase of the menstrual cycle. It is speculated that this property of RU 486 could be utilized in the design of an estrogen-free combined oral contraceptives.

Intravaginal administration of RU 486 in humans and rats: inadequate absorption in humans

Vaginal absorption of the antiprogesterone steroid RU 486 was studied in humans and rats. In rats, RU 486 was sufficiently absorbed to terminate early pregnancy following vaginal, oral or intramuscular administration. The quantitation of RU 486 in serum showed that the ratios of the areas under the concentration curves per mg administered were 1:2.8:3.4 for the vaginal, intramuscular and oral routes, respectively. Female volunteers received RU 486 vaginally in polyethylene glycol (PEG) suppositories, in tampons and in oil solution. Following vaginal (PEG-suppository) and oral administration of 100 mg of RU 486, the ratio of the areas under the serum concentration curves was 1:56, respectively. From tampons and oil, RU 486 was absorbed in a similar manner to that of the PEG-suppositories, resulting in nanomolar serum concentrations. In humans no biological effects were noted following vaginal administration of RU 486. These data suggest that vaginal release of RU 486 is not a successful route of administration in humans.

Metabolism and serum binding of RU 486 in women after various single doses

The metabolism of RU 486 was studied in female volunteers following a single oral administration of 100, 400, 600 or 800 mg of RU 486. The serum concentrations of RU 486 were generally not affected by the dose within the range examined and they stayed at micromolar concentrations during the 48 h studied. RU 486 was metabolized extensively in a dose-dependent manner by two-step demethylation, and by hydroxylation. Serum levels of the monodemethylated metabolite always exceeded those of RU 486. The concentrations of the didemethylated and hydroxylated metabolites equalled or exceeded those of RU 486 when the ingested dose was 400 mg or more. Monodemethylation and hydroxylation were rapid high-capacity reactions, whereas didemethylation was a lower-capacity reaction. In each group of different dosage, positive correlations were found between the individual mean alpha 1-acid glycoprotein (AAG) concentrations and the peak concentration of RU 486 measured at 1-2 h, versus the plateau concentration of RU 486 measured at 6 h. The in-vitro studies showed that the specific serum transport protein of RU 486, AAG, was saturated by RU 486 concentrations exceeding 2.5 microM. In serum at 40 nM and 2.5 microM RU 486 concentrations, 2.7% and 2.4%, respectively, of [3H]RU 486 was not protein bound. Purified AAG in phosphate buffer was able to bind [3H]RU 486 in a similar manner to that of serum. Thus our results suggest that AAG regulates in part the serum concentrations of RU 486, and RU 486 exceeding the specific serum transport capacity is effectively metabolized.

Pharmacokinetic properties of the antiglucocorticoid and antiprogesterone steroid RU 486 in man

RU 486 (17 beta-hydroxy-11 beta-[4-dimethylamino phenyl]-17 alpha-[1-propynyl]estra-4,9-dien-3-one) is a clinically useful glucocorticoid and progesterone antagonist. The authors studied the pharmacokinetic properties of this drug in normal volunteers and patients with Cushing's syndrome using a rat progesterone radioreceptor assay. This assay gave values similar to those obtained with a rat glucocorticoid radioreceptor assay. After a single oral dose of 25 mg/kg (n = 11) or 10 mg/kg (n = 11) to normal volunteers, plasma concentrations of progesterone receptor-reactive material reached maximal levels of 754 +/- 288 (mean +/- S.D.) and 517 +/- 183 micrograms/dl. This occurred at 3.1 +/- 1.9 and 2.5 +/- 1.0 h, respectively. The respective apparent plasma half-lives were 19.2 +/- 7.0 and 20.6 +/- 7.7 h. Four patients with Cushing's syndrome treated chronically (10-20 mg/kg/day) had relatively constant plasma levels of receptor reactivity ranging from 506 to 1184 micrograms/dl. Chromatographic characterization of circulating receptor reactivity showed that the active fraction corresponded to RU 486 and its hydrophilic N-mono- and N-didemethylated metabolites. Less than 0.5% of the daily dose was excreted in the urine of two of these patients as receptor reactivity. The drug bound extensively to circulating albumin, which competed with the glucocorticoid receptor of intact human mononuclear leukocytes for [3H]RU 486 in a concentration-dependent manner.

[Effects of ovarian wedge resection (WR) and spironolactone administration on pulsatile LH release and serum steroid hormone levels in women with polycystic ovarian disease]

The exact mechanism(s) by which WR induces ovulation in women with PCOD is still uncertain. The aim of this study is to observe the change in sex steroids and pulsatile LH release (pul-LH-R) after WR. Before and either 7-8 days after the surgery (n = 8) or after 30 days of spironolactone treatment (n = 4), serum LH levels were measured every 15 min for 2-4 hours in PCOD women. Sex steroids were radioimmunoassayed before, and 3-4 and 7-8 days after WR. Testosterone (T) and androstenedione (A) in 7 women in whom spontaneous ovulation occurred after WR decreased significantly either 3-4 or 7-8 days after the surgery (p less than 0.001). Estrone decreased significantly (p less than 0.001) 7-8 days after the operation. The mean level of LH after WR in the 7 women decreased significantly (p less than 0.001). Furthermore, significant decreases both in the mean values of LH pulse amplitude (p less than 0.001) and frequency (p less than 0.01) were observed after WR. Ovulation occurred after 45 and 58 days of spironolactone administration in 2 PCOD women who showed changes in pul-LH-R and a drop in serum testosterone levels after 30 days of treatment. The data suggested that changes in pul-LH-R and decreased sex steroids after WR seemed to play key roles in the mechanism(s) by which WR induces ovulation.

Plasma concentrations and receptor binding of RU 486 and its metabolites in humans

Using Chromosorb chromatography and HPLC, we measured the plasma concentrations of RU 486, and its monodemethylated (RU 42633), didemethylated (RU 42848) and alcoholic nondemethylated (RU 42698) metabolites up to 72 h following oral ingestion of 100 mg of RU 486 by five female volunteers. The peak plasma level of RU 486 (4.5 mumol/l) occurred within 1 h after ingestion of the compound; at this point significant amounts of the metabolites were also present in the plasma. After the initial redistribution within 6 h the plasma concentrations of RU 486 and three of its metabolites measured remained stable for 24 h. Concentrations of the monodomethylated metabolite exceeded those of the parent steroid during the time period measured, whereas the concentrations of the didemethylated and alcoholic metabolites were lower than those of RU 486, but still notable. At 72 h the concentrations of all the four steroids were still in the micromolar range. The relative binding affinities of these metabolites to human endometrial and myometrial progesterone receptors as well as to human placental glucocorticoid receptors were determined in vitro. The affinity of RU 486 for the human uterine progesterone receptor (Kd = 1.3 X 10(-9) M for RU 486) was higher than that of progesterone but lower than that of ORG-2058, a potent synthetic progestin. The relative binding affinities of the monodemethylated, alcoholic and didemethylated metabolites to the progesterone receptor were 21, 15 and 9%, respectively, compared with the parent compound RU 486; each was lower than that of progesterone (43%). RU 486 had an approx. 4-fold higher relative binding affinity to the glucocorticoid receptor than dexamethasone. Interestingly, the relative binding affinities of the metabolites studied to the human glucocorticoid receptor exceeded those of dexamethasone or cortisol. Compared with the parent compound RU 486, they were 61, 48 and 45% for the monodemethylated, alcoholic and didemethylated metabolites, respectively; each was higher than that of dexamethasone (23%). The affinity of dexamethasone to the human glucocorticoid receptor was 1.6 X 10(-9) M. These data indicate that the pool of certain metabolites of RU 486 may contribute to a significant extent to the antiprogestagenic (23-33%) and even greater extent to the antiglucocorticoid (47-61%) effects of RU 486.

Quantitation of RU 486 in human plasma by HPLC and RIA after column chromatography

Chromosorb column chromatography was used for separation of RU 486 from its immunologically cross-reacting metabolites prior to quantitative analysis by radioimmunoassay (RIA) or high-performance-liquid chromatography (HPLC). The results of the two assay methods were in good agreement with each other (r = 0.99, n = 29). The retention time of RU 486 in our HPLC system was 2.5 min. Plasma concentrations of RU 486 were measured by HPLC up to 48 h following single oral administration of 100, 400, 600 and 800 mg of RU 486 to female volunteers. The plasma peak concentrations (2.0-2.5 micrograms/ml) were reached within the first hour. After redistribution, the plasma concentrations of RU 486 were not significantly affected by the doses studied but remained in the same range throughout the 48 hours. The plasma half-life between 24 and 48 hours was 27 hours or more. We conclude that HPLC is valuable in studies on the metabolism and pharmacokinetics of RU 486, but a less laborious RIA method after Chromosorb column chromatography is suitable and gives reliable results in large-scale clinical studies.

Plasma levels of antiprogestin RU 486 following oral administration to non-pregnant and early pregnant women

RU 486 is a synthetic steroid which acts as an antiprogestin at the receptor level. The clinical usefulness of the compound for menstrual regulation and termination of early pregnancy is currently being evaluated. The aim of the present study was to determine the plasma levels of RU 486 following the oral administration of the compound to 42 pregnant and 10 non-pregnant women. The levels of RU 486 were measured by a radioimmunoassay method which uses chromatography on Sephadex LH 20 columns. The identity of the compound assayed as RU 486 was confirmed, but the presence of small amounts of two highly cross-reacting metabolites (monodemethyl and didemethyl RU 486) in the analyzed fractions could not be excluded. Following the ingestion of a single tablet containing 25 and 50 mg of the compound, a peak plasma value of approximately 3.5 to 4.0 mumol/l in both the pregnant and non-pregnant subjects was reached one to two hours later. The half-lives of elimination were about 20 hours in both the pregnant and the non-pregnant women. Following the repeated oral administration of 50, 100 or 200 mg of RU 486 daily for four days, maximum plasma levels of 2.9, 4.5 and 5.4 mumol/l, respectively, were found. Thus, the increase in plasma levels was not directly proportional to the increase in the dose. No accumulation of RU 486 in the plasma was found, even when the duration of treatment was prolonged to six days. The data partly explain the reported lack of relation between ingested dose and frequency of induced abortion and they may be useful for designing future studies on the use of compound to prevent implantation, induce menstruation or terminate an early pregnancy.

Pharmacokinetics of the progesterone antagonist 17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)-17 alpha-(1-propynyl) estra-4,9-dien-3-one in the rabbit

Pharmacokinetic characteristics of compound RU 486 (17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)-17 alpha-(1-propynyl)estra-4,9-dien-3-one) were investigated in 6 immature estrogenized female rabbits. A dose of 3.4 mg/kg was administered either intravenously or orally, in both cases together with 3H-RU 486 (13.4 muCi/kg). The concentration of RU 486 was measured in blood plasma following isolation by thin-layer chromatography. The concentration of ether-extractable metabolites was obtained from the difference between the total ether-extractable radioactivity and the radioactivity of the isolated RU 486. Following the i.v. administration it was found that the disposition of RU 486 could be described by a biexponential curve. The half-life of the slow disposition phase of RU 486 was significantly lower (t1/2 = 52 min: P greater than 0.05) than those of RU 486 metabolites (t1/2 = 99 min). High apparent volumes of distribution of RU 486 and RU 486 metabolites (5.8 and 6.0 l/kg, respectively) indicated a high extravascular binding. Following the oral administration in oil solution, RU 486 could not be found in plasma in reliably detectable amounts due to a poor absorption and a probable first-pass effect. In the measurements of the "total RU 486" (sum of RU 486 and ether-extractable metabolites), a similar rate of terminal disposition was found for both routes of administration.

[Protein binding of steroids]

The role of protein-binding in the physiology of steroids is of great complexity. The following are envisaged: the types of protein, methods of binding and the affinity of steroids for proteins, and the variations in free fraction according to plasma protein levels; the functions of binding proteins on the activity and clearance of steroids as well as on the peripheral conversion of androgens; the factors which influence variations in binding protein levels and in particular the influence of circulating levels of natural hormones and the influence of hormone treatment.

Steroid secretion by the postmenopausal ovary

The concentrations of certain steroids in arterial and ovarian venous blood were measured in 42 postmenopausal women undergoing hysterectomy for uterine disease. A concentration gradient across the ovary was found for testosterone in 21 women, for androstenedione in 16, for estradiol in 15, for estrone in 8, and for dehydroepiandrosterone in 3. On the basis of postualated ovarian blood blow the gradient would result in a major contribution to the blood production rate for testosterone in about 50% of women and for estradiol in less than 20%. For androstenedione, dehydroepiandrosterone, and estrone the gradients did not signify important ovarian secretion. There was no evidence for secretion of dihydrotestosterone, estrone sulfate, or dehydroepiandrosterone sulfate. There were no apparent clinical correlates to indicate in which women the ovary was secreting steroids.

Radioimmunoassays for free and conjugated trienbolone and for trienbolone acetate in bovine tissue and plasma samples

A specific, sensitive, precise and accurate radioimmunoassay has been developed for the quantitation of the synthetic anabolic steroid trienbolone acetate (TBA) and its major metabolites, free and conjugated trienbolone (TBOH) in bovine tissues and plasma. With the extraction procedure described unspecific interference with the antigen-antibody reaction could be ruled out. The assay can significantly detect amounts of more than 40 pg TBOH and 70 pg TBA. 0.1 - 2.0 g tissue and 0.1 - 1 ml plasma are sufficient for 1 determination. Residues (range 0.1 -2.0 ng/g) were still present in calves 69 days after implantation of "Revalor" (20 mg estradiol-17beta and 140 mg TBA) with the highest concentrations found in liver and TBA could only be quantitated in fat.

Studies on the pattern of circulating steroids in the normal menstrual cycle. I. Simultaneous assays of progesterone, pregnenolone, dehydroepiandrosterone, testosterone, dihydrotestosterone, androstenedione, oestradiol and oestrone

In an attempt to analyze the multiple changes and interactions in circulating steroid levels in the peri-ovulatory and peri-menstrual periods, the plasma levels of immunoreactive luteinizing hormone (LH), progesterone and unconjugated pregnenolone, dehydroepiandrosterone, testosterone, oestradiol and oestrone were assayed daily during a complete cycle in 17 normally menstruating women. In 14 of the 17 subjects studied androstenedione and unconjugated dihydrotestosterone were also estimated. The day of the LH-peak and the first day of menstruation, respectively, were used to synchronize the peri-ovulatory and peri-menstrual plasma levels of the various steroids. With the exception of dehydroepiandrosterone and dihydrotestosterone, the plasma levels of all steroids exhibited significant, but different changes during the cycle. Testosterone levels showed a slight but significant increase around the LH-peak, whereas the levels of pregnenolone and androstenedione were higher in the post-ovulatory than in the pre-ovulation periods. The levels of oestradiol and oestrone, as well as the ratios of oestradiol to oestrone gradually increased from the low values observed in the early proliferative phase to pre-ovulatory peak values. The relationship between peaks of oestradiol and oestrone and that of LH exhibited great individual variation. The same was true for the individual oestradiol to oestrone ratios. The combination of several steroidal signals did not improve the predictive value of the analyses. However, an increase of individual progesterone values by at least 0.35 ng/ml from the day preceding the LH-peak to the day of the LH-peak was observed in 13 of the 17 subjects. It is suggested that for the early detection of the LH surge and prediction of the subsequent ovulation daily assays of plasma progesterone are of more value than the assay of the other steroids investigated.