Metabolism of estrogens in breast cancer.

PIP: This extensive literature compilation reviews major studies on estrogen metabolism in cancer, studies which have led to proposed possible etiological roles of estrogens in human breast cancer. Urinary and plasma estrogen excretion patterns and profiles in women with breast cancer are the topics of part 1. Studies of estrogen profiles in women who are at high-risk for breast cancer are critiqued. The estriol hypothesis is presented and criticised in a chapter. The effects of endocrine ablation on urinary estrogen profiles in breast cancer patients are compiled. Production and metabolism of estrogens in women with breast cancer are rendered, including in vivo biotransformation rates and in vitro transformation data. And the search for estrogen metabolites in women with breast cancer is reviewed. In conclusion it is obvious that the question of whether breast cancer patients have an abnormal metabolism of estrogen has not been answered, but further investigations of estrogen metabolism in breast cancer should be continued because: 1) the possibility that estrogens are carcinogenic has not been ruled out; 2) receptors have been discovered which do correlate with hormone dependency of tumors; 3) present evidence suggests that neoplasm may induce abnormal estrogen metabolism; 4) directional changes of estrogen metabolism that occur in pregnancy may also occur in women with target tissue neoplasia; 5) hepatic tissue's relationship to breast cancer has not received attention; and 6) the role of peripheral aromatization in the pathogenesis of mammary cancer is not yet understood.^ieng

Serum medroxyprogesterone acetate (MPA) concentrations and ovarian function following intramuscular injection of depo-MPA.

A sensitive radioimmunoassay measuring serum medroxyprogesterone acetate (MPA) has been developed in order to measure and correlate serum MPA concentrations and ovarian function in women following im administration of deop-MPA (DMPA), employing goat anti-MPA-3-(O-carboxymethyl) oxime-bovine serum albumin and MPA-3-(O-carboxymethyl) imino-125I-iodohistamine. In the 3 women studied, im injection of 150 mg of DMPA yielded brief initial serum MPA concentrations ranging from 1.5 to 3 ng/ml for a few days. Serum MPA concentrations gradually declined and remained relatively constant at about 1 ng/ml for 2 to 3 months, declined gradually thereafter reaching 0.2 ng/ml during the 6th month and became undetectable (less than 0.02 ng/ml) about 7-1/2 to 9 months following administration. Serum estradiol remained at early to midfollicular phase levels for 4 to 6 months after DMPA injection and rose to preovulatory levels when serum MPA levels fell below 0.5 to 0.25 ng/ml. Ovulation, however, as evidenced by serum progesterone concentrations did not occur, apparently due to suppression of the LH peak by positive feedback inhibition. Prolonged inhibition of cyclic ovarian function following DMPA injection is caused by slow MPA absorption and persists until serum MPA levels have decreased below 0.1 ng/ml or become undetectable about 7 to 9 months after DMPA administration.

PIP: Serum medroxyprogesterone acetate (MPA) concentrations were measured by a newly developed, highly sensitive, radioimmunoassay technique, and ovarian function was evaluated in 3 women after a single im injection of MPA (150 mg). Initial MPA concentrations ranged from 1.5 to 3 ng/ml for the 1st few days, and then gradually declined to a relatively constant level of about 1 ng/ml for 2-3 months. During the 6th month, MPA concentrations had declined to about .2 ng/ml, and became undetectable between 7!-9 months. Serum estradiol levels remained at early or midfollicurlar phase values for 4-6 months following injection, and then increased to preovulatory values (.25-.5 ng/ml). However, ovulation did not occur as determined by serum progesterone concentrations. Prolonged suppression of ovarian function by depo-MPA is due to the slow release of MPA; from the injection site.

Existence of multiple peaks in plasma ethinyl estradiol and norethindrone after oral administration of a contraceptive pill.

Previous measurements of plasma ethinyl estradiol (EE2) and norethindrone (NE) over 24 h after oral administration of a contraceptive pill have demonstrated a single steroid peak occurring 1-2 h after pill ingestion, with a gradual decline over the next 22 h. In the present study plasma concentrations of EE2 and NE were measured 0, 0.5, 0.75, 1, 2, 4, 12, and 24 h after oral ingestion of a contraceptive pill containing 35 micrograms EE2 and 1 mg NE at 0, 3, 6, and 9 months of use in 58 normal healthy women. Contrary to previous reports, analysis of the 464 steroid curves (58 subjects x 4 time periods x 2 steroids) revealed the presence of multiple hormone peaks. Two peaks of EE2 were identified in 44.8% of women during the first pill cycle and in 75.9%, 55.2%, and 67.2% of women after 3, 6, and 9 months of pill use. Two hormone peaks of NE were observed in 29.3% of women during the first cycle and in 36.2%, 50%, and 44.8% at 3, 6, and 9 months, respectively. Existence of these multiple peaks at the frequency observed has not previously been reported. Further quantification of the frequency and magnitude of these peaks could be helpful in explaining differences in biological responses associated with pill use.

The effect of olestra on systemic levels of oral contraceptives.

The effect of olestra, a nonabsorbable, noncaloric fat replacement, on the absorption and efficacy of a highly lipophilic oral contraceptive was investigated in a double-blind, placebo-controlled crossover study with 28 women. Subjects consumed 18 gm/day olestra for 28 days while taking an oral contraceptive containing 300 micrograms of norgestrel and 30 micrograms ethinyl estradiol (Lo/Ovral-28). Blood taken on days 12 to 14 of the treatment cycles was analyzed for ethinyl estradiol and norgestrel. There was no statistically significant difference in time to attain maximum concentration, maximum concentration, or area under the concentration-time curve between the olestra and placebo treatments for either drug component. Measurements of serum progesterone indicated that olestra ingestion did not reduce efficacy as indicated by ovulation. The data show that ingestion of 18 gm/day olestra did not affect the absorption or efficacy of the highly lipophilic oral contraceptive.

An X-ray crystallographic study of the nonsteroidal contraceptive agent centchroman.

We have determined an X-ray crystal structure for the N-methyl iodide derivative of the nonsteroidal contraceptive centchroman. The pendant aromatic substituents on C-3 and C-4 of the chroman system are nearly perpendicular to the plane of the chroman system, an orientation expected in such a chroman, but perturbed to some degree by the gem dimethyl substituents at C-2. Structural superposition with other nonsteroidal antiestrogens, tamoxifen and nafoxidine, shows a similar disposition of the tertiary amine side chains responsible for antagonist activity. The aryl rings also show good superposition, but in contrast to tamoxifen and nafoxidine, which have the potential for ring double bond conjugation, the centchroman aryl rings show a larger dihedral twist. While different superpositions between the enantiomers of centchroman and the bioactive enantiomer of estradiol (d-estradiol, 8 beta,9 alpha,13 beta,14 alpha,17 beta) are possible, when the chroman ring system is positioned over the AB rings of estradiol, then (3R,4R)-centchroman makes the best fit. The aryl substituents in both enantiomers make comparable overlays with the steroidal skeleton, but the axial methyl group at C-2 in (3R,4R)-centchroman is directed downward along the C-7 alpha axis of estradiol, a site where many substituents are known to be well tolerated by the estrogen receptor, while in the 3S,4S-enantiomer, this methyl group is projected upward. Thus, we suggest that the bioactive l-enantiomer of centchroman will have the 3R,4R absolute configuration.

17 -Propadienyl, 17 -propynyl, and 17 -trifluoropropynyl analogs of 6,6-difluoronorethindrone.

PIP: The synthesis of analogs of 6,6-difluoronorethindrone (la) is reported. The new compounds, each of which are potent oral progestational agents, are ( )-6,6-difluoronorgestrel (lb), 17 beta-hydroxy-6,6-difluoro-17alpha-propadienyl-4-estren-3-one (lc), 17beta-hydroxy-6,6-difluoro-17alpha-(1-propynyl)-4-estren-3-one (ld), and 17 beta-hydroxy-6,6-difluoro-17alpha-(3,3,3-trifluoropropynyl)-4-estren-3-o ne (le). The 6,6-gem-difluoro group is an important means for enhancing the progestational activity of parent compounds. Compounds lc,ld, and le were prepared from a common precursor, 6,6-difluoro-4-estrene-3,17-dione 3-ethylene ketal. The findings indicate that 6,6-difluoro steroids are stable towards a variety of reagents. The experimental procedures are summarized.^ieng

1-Trifluoromethyl-1,2,2-triphenylethylenes. Synthesis and postcoital antifertility activity.

PIP: The synthesis of a series of triphenylethlenes with CF(3) groups placed directly on the ethylene carbon is described, and the postcoital and uterotropic activities of these 1-trifluoromethyl-1,2,2-triphenylethylenes are determined. The parent compound and 3 substituted analogs were prepared by the stepwise replacement of the vinylic F atoms of hexafluoropropene with aryl groups from ArLi reagents. The postcoital antifertility and uterotrophic activities in the rat were determined by treating rats with induced precocious puberty with the synthesized compounds for 6 days after mating occurred. The most potent compound of this series was trans-p-methyoxy-alpha-phenyl-alpha'-(trifluoromethyl) stilbene.^ieng

Preparation and progestational activity of 6-cyano-16-methylene-17 -hydroxy-4,6-pregnadiene-3,20-dione 17-acetate and related compounds.

PIP: The synthesis of of 6-formyl-6-dehydro-16-methylene-17alpha-acetoxyprogesterone (3) and of 6-cyano-6-dehydro-16-methylene-17alpha-acetoxyprogesterone (4) is reported. The preparation of (3) was carried out by converting 3-ethoxy-16-methylene-17alpha-YDROXY-3,5PREGNADIEN-20-ONE 17-acetate (5) by the Vilsmeier reaction to 3-ethoxy-6-formyl-16-methylene-17alpha-hydroxy-3,5-pregnadien-20-one 17-acetate (6). On treatment with dichlorodicyanobenzoquinone (DDQ) in 95% aqueous acetone (6) afforded the desired (3) in 45% yield. The 6-cyano derivative (4) was prepared by reacting (6) with hydroxylamine to give 3-ethoxy-6-oximinomethyl-16-methylene-17alpha-hydroxy-3, 5-pregnadien-20-one 17-acetate; this compound on treatment with DDQ in 95% aqueous acetone gave 6-oximinomethyl-16-methylene-17alpha-hydroxy-4, 6-pregnadien-3,20-dione 17-acetate (9) in 68% yield. Reaction of (9) with phosphorus oxychloride in pyridine afforded the desired 6-cyano dienone (4) in 70% yield. Progestational activity of (3) was the same as that of progesterone, while that of (4) was 5.8 as great.^ieng

Synthesis and biological activity of 17-esters of 6-dehydro-16-methylene-17 -hydroxyprogesterones.

PIP: Synthesis and biological activity of 17-esters of 6-dehydro-16-methylene-17 alpha-hydroxyprogesterone are presented. A systematic study of the influence of the alteration of halogen at 6 and the acyl group at 17 on the progestational and antiandrogenic activities of the resulting structures is described. A convenient general method for synthesis of all of the members of the generic family from the precursors in common is described. It is believed that 6-chloro-16-methylene-17 alpha-hydroxy-4,6-pregnadiene 17-acetate, because of its structural similarity to chlormadinone acetate and its high progestational potency, will perform as a contraceptive at perhaps a lower dose than that of chlormadinone acetate.^ieng

Synthesis and antifertility activity of some oximinoandrostenes.

PIP: 3-aza-A-homo steroids have been of interest to these authors in their efforts to develop novel progestational agents. Because it exhibits antifertility activity both in humans and animals, 17alpha-ethynyl-19-nortestosterone (norethindrone) was chosen to undergo molecular modification. The syntheses of a number of oximino and 3-aza-A-homoandrostenes are described in the experimental section of the article. The progestational responses of the compounds were tested through the observation of rabbit uteri. The capacity of a compound to inhibit fertility in rate was noted from the minimum effective dose, i.e., the amount of compound in mg/kg per day which completely suppressed litter production (compound given to both male and female). Because of the suspicion that the oximino steroids were acting postcoitally, 17-beta-acetoxy-19-norandrost-4-en-3-one oxime was studied for its postcoital activity in rats. The postcoital antifertility action of the compound appears to be due to lytic degeneration of zygotes and/or their rapid expulsion from the reproductive tract. Some structure-function observations are made concerning the various compounds.^ieng

The pharmacokinetics of norethisterone in the rabbit and rat after systemic and oral administration: effect of phenobarbitone [proceedings].

PIP: The pharmacokinetics of norethisterone in the rabbit and the rat after systemic and oral administration and the effect of phenobarbitone on pharmicokinetic parameters is presented. Norethisterone was given by iv and oral routes (85 mcg/kg) in the rabbit and by portal administration in the rat. Blood samples were collected over 24 hours in the rabbit and over 2 hours in the rat. Norethisterone was measured in plasma by radioimmunoassay. The plasma concentration-time curve was resolved into values for "fast disposition" half-life, "slow disposition" half-life, and the area under the curve (AUC). In the rabbit, AUC after oral administration was 53% of iv administration, while in the rat the AUC after portal administration was 32% of that after iv administration. In the rabbit phenobarbitone was without effect on plasma norethisterone concentrations after iv administration but significantly reduced the plasma concentration after oral administration. In the rat phenobarbitone had little effect on plasma norethisterone concentrations despite evidence of enzyme induction.^ieng

Effect of the progestogens, gestodene, 3-keto desogestrel, levonorgestrel, norethisterone and norgestimate on the oxidation of ethinyloestradiol and other substrates by human liver microsomes.

A number of different progestogens, levonorgestrel (LNG), norethisterone (NET), gestodene (GSD), desogestrel (DG) and norgestimate (NORG) are used in combination with the oestrogen ethinyloestradiol (EE2) in oral contraceptive steroid preparations. All the progestogens are acetylenic steroids and previous studies have indicated the potential of acetylenic steroids to cause mechanism-based or "suicide" inactivation of cytochrome P-450. We have compared the effects of the different progestogens on EE2 2-hydroxylation (a reaction catalyzed by enzymes from the P-450IIC, P-450IIIA and P-450IIE gene families) and also the oxidative metabolism of other drug substrates (cyclosporin, diazepam, tolbutamide) by human liver microsomes. On coincubation with EE2 as substrate, GSD, 3-keto desogestrel (3-KD, the active metabolite of desogestrel) and LNG produced some concentration-dependent inhibition of EE2 2-hydroxylation (maximum 32% inhibition at 100 microM 3-keto desogestrel). Ki values determined for GSD and 3-KD were 98.5 +/- 12.3 and 93.2 +/- 10.3 microM (mean +/- SD; n = 4), respectively. Preincubation of progestogens in a small volume (50 microliters) incubation for 30 min in the presence of an NADPH-generating system enhanced the inhibitory potential of all the steroids (at 100 microM, inhibition was for GSD 39%, 3-KD 46%, LNG 46%, NET 51% and NORG 43%). Inhibitory effects were therefore comparable and also similar to the macrolide antibiotic troleandomycin. The most marked inhibition seen was of diazepam N-demethylation and hydroxylation by GSD (71 and 57%, respectively) and 3-KD (62 and 50%, respectively). In preincubation studies involving cyclosporin as the substrate, the order of inhibitory potency was GSD greater than 3-KD greater than NET greater than LNG for production of both metabolite M17 and M21. The results of the study indicate that all the progestogens in common use have the propensity to inhibit a number of oxidative pathways but there is little evidence for one progestogen being more markedly inhibitory than others.

Endocrine properties and clinical application of danazol.

PIP: Danazol, a heterocyclic steroid related chemically to 17 alpha-ethinyltestosterone (ethisterone), is currently approved by the FDA for treatment of endometriosis only. However, other clinical applications of the drug may be found for both endocrine and nonendocrine disorders. Hence, the literature of danazol is reviewed. Included are discussions of the chemical structure and biological properties of danazol, which has a basic cyclopentenophenanthrene configuration characteristic of all steroids, and exerts its effects at a subcellular level. Its metabolism and excretion have been studied in animals extensively and in humans via tritiated danazol administration. The drug is well-absorbed from the gastrointestinal system and is rapidly metabolized. Over 60 metaboites have been associated with the metabolic endproduct of tritiated danazol, but only 6 are recognized as metabolites of the drug. Its antigonadotropic effect receives the most attention in the review. In experimental animals various doses of danazol have suppressed gonadal weight (rats), suppressed pituitary gonadotropins (rats and humans), suppressed gonadotropin-releasing hormones (rats and humans), suppressed fertility (rats and rhesus monkeys), and suppressed gonadal steroidogenesis (rats and hamsters). Other biological properties of danazol, besides its primary one of suppression of gonadotropic effect, are related to its androgenicity. Various conceivable clinical applications of danazol are discussed, and its use in therapy of endometriosis is outlined and discussed in detail.^ieng

Accumulation of ethinylestradiol in blood and endometrium of women taking oral contraceptives: the sequential therapy.

A radioimmunoassay to quantitate ethinylestradiol (EE-2) in both plasma and endometrium is described. In 29 women under sequential oral contraceptive therapy (chlormadinone acetate, 2 mg, plus mestranol, 80 microgram) for 6 to 84 months, a single blood sample and a single endometrial sample were simultaneously obtained on different days of the pseudomenstrual cycle. In 24 women under 40 years of age the mean plasma EE-2 concentrations were similar during the first (989 +/- 94 pg/ml) and the second half of the cycle (1053 +/- 186 pg/ml) (P greater than 0.05). A similar finding was observed with regard to mean endometrial EE-2 concentrations (3.55 +/- 2.1 and 5.89 +/- 1.7 microgram/gm of wet tissue, respectively). On the other hand, five women over 40 years of age had plasma EE-2 concentrations similar to those of the previous group, but the mean endometrial EE-2 concentrations was 0.9 +/- 0.6 microgram/gm of wet tissue (P less than 0.05). Although plasma follicle-stimulating hormone and luteinizing hormone did not show midcycle peak values, complete suppression of both gonadotropins was not observed. These results show that endometrium has a great ability to concentrate EE-2, and this ability seems to be greater in women below age 40 than above. Whether or not this observation might be related to the known higher incidence of endometrial cancer in women less than 40 years old who have been under chronic sequential oral contraceptive therapy cannot be disclosed from this limited number of determinations.

PIP: A radioimmunoassay to quantitate ethinylestradiol (EE-2) in both plasma and endometrium is described. In 29 women receiving sequential oral contraceptive (OC) therapy (chlormadinone acetate, 2 mg plus mestranol, 80 mcg) for 6-84 months, a single blood sample and a single endometrial sample were simultaneously obtained on different days of the pseudomenstrual cycle. In 24 women under 40 years of age, the mean plasma EE-2 concentrations were similar during the 1st (989 +/- 94 pg/ml) and the 2nd half of the cycle (1053 +/- 186 pg/ml) (P . 0.05). A similar finding was observed with regard to mean endometrial EE-2 concentrations (3.55 +/- 2.1 and 5.89 +/- 1.7 mcg/gm or wet tissue, respectively). On the other hand, 5 women over 40 years of age had plasma EE-2 concentrations similar to those of the previous group, but the mean endometrial EE-2 concentration was 0.9 +/- 0.6 mcg/gm of wet tissue (P .05). Although plasma follicle stimulating hormone and luteinizing hormone did not show midcycle peak values, complete suppression of both gonadotropins was not observed. These results show that endometrium has a great ability to concentrate EE-2, and this ability seems to be greater in women below age 40 than above. Whether or not this observation might be related to the known higher incidence of endometrial cancer in women less than 40 years old who have been under chronic sequential OC therapy cannot be disclosed from this limited number of determinations. Future study might uncover competitive effects between synthetic steroids and endogenous hormones in the endometrium.

Variation of ethinylestradiol blood levels among healthy women using oral contraceptives.

Data concerning ethinylestradiol (EE) blood levels among 93 healthy women using oral contraceptives are presented. Seventy-two per cent of the observed variation in EE blood levels was unexplainable on the basis of time since ingestion of the last oral contraceptive, day of menstrual cycle, race, age, weight, height, blood pressure, cigarette consumption, alcohol consumption, diurnal variation, or lifetime use of oral contraceptives.

PIP: This 2-fold investigation studied 1) the extent to which women vary in blood levels of ethinylestradiol (EE) after ingesting oral contraceptives (OCs) containing similar amounts of EE or mestranol (ME), which is metabolized to EE; and 2) whatever variations might be accountable on the basis of physical, behavioral, or other characteristics. 93 healthy OC users were given either OCs with 50 mcg of ME (84 subjects) of 50 mcg of EE (9 subjects). Linear regression was used to determine relevance of variation in EE blood levels based on hours since pill ingestion, day of menstrual cycle, or any other variables. Hours since OC showed the strongest relationship to log EE, accounting for 25% of the variation. Another 3% could be accounted for by day of menstrual cycle. The remaining 72% of observed variation in EE levels could not be explained in terms of time since ingestion of last OC, day of menstrual cycle, race, age, weight, height, or use-duration of OCs.

Subcutaneous bioabsorbable pellets of norethindrone for contraception in women: Phase I. Clinical study.

Ten healthy, normally menstruating female volunteers participated in a 1-year phase I clinical study in which subcutaneous pellet implants of norethindrone (NET) were employed as a low-dose and long-acting potential contraceptive. Two NET pellets were implanted subcutaneously by the aid of a trocar in the forearm of each volunteer on the fifth day after the start of menstrual bleeding. Serum levels of NET, follicle-stimulating hormone, luteinizing hormone, 17 beta-estradiol, and progesterone were determined weekly by radioimmunoassay. The daily NET release from the pellets, based on mean values (+/- standard error of the mean) in five subjects was 79.4 +/- 7.6 micrograms. The mean serum NET level was initially 1.0 +/- 0.34 ng/ml; thereafter, it gradually lowered during the 343 days of the study period to the level of 0.43 +/- 0.09 ng/ml. The ovarian response, days of bleeding, and cycle lengths with continuously sustained release of NET from the pellets were similar to those observed in women taking the daily oral "minipill" of 300 micrograms NET. The results of the phase I study suggest that NET pellet implants may provide a simple and acceptable approach to long-term contraception in women.

Ovarian function in amenorrheic and menstruating users of a levonorgestrel-releasing intrauterine device.

The ovarian function of 20 healthy users of a levonorgestrel-releasing intrauterine device was studied by measurements of plasma estradiol, progesterone, and levonorgestrel concentrations. Eight subjects were amenorrheic, and 12 had regular menstrual bleeding. Seventy-five percent of the subjects in both groups had ovulatory cycles. There was no difference between the mean levonorgestrel concentrations in the amenorrheic and regularly menstruating subjects. Estradiol function was undisturbed in the amenorrheic subjects with ovulatory cycles. The effect of levonorgestrel as a cause of amenorrhea is thought to be mainly of local nature. The intrauterine administration of levonorgestrel had only an occasional and weak effect on ovarian function.

The use of biodegradable norethisterone implants as a 6-month contraceptive system.

The effects of a 6-month contraceptive system of biodegradable norethisterone (NET) implants on the menstrual cycle, estradiol and progesterone levels, the presence of side effects, its contraceptive effectiveness, and the NET levels achieved were studied in a group of nine women. There was practically no disruption of the menstrual cycle and no important side effects. Ovulation was inhibited in four subjects, and another four subjects remained ovulatory. In all the subjects a cyclic secretion of estradiol was maintained. No pregnancies occurred. The circulatory levels of NET were very stable throughout the 6-month period of implant use.

The mechanism of action of an antifertility vaccine in the rhesus monkey: reversal of the effects of antisera to the beta-subunit of ovine luteinizing hormone by medroxyprogesterone acetate.

Active immunization of female rhesus monkeys with the beta-subunit of ovine luteinizing hormone )oLH beta) significantly reduced their fertility. To determine whether the major action of the vaccine was interruption of pregnancy, by suppression of "corpus luteum rescue," or inhibition of ovulation, we administered the progestational agent medroxyprogesterone acetate (MPA) from day 4 through day 40 after mating. In the untreated immunized group, the pregnancy rate was significantly below that of control monkeys. MPA treatment restored the fertility rate of immunized animals to that of the control group. These results strongly support the assumption that the antifertility action of antibodies of oLH beta is due to prevention of corpus luteum rescue. Whether the lack of corpus luteum rescue resulted because of neutralization of rhesus monkey chorionic gonadotropin or from a defective corpus luteum, as is found in animals with short luteal phases, cannot be determined from these studies. The successful reversal of the antifertility effect, however, suggests that the circulating antibodies do not interfere with normal ovulation or with the normal development and implantation of the blastocyst.

PIP: Active immunization of female rhesus monkeys with the beta-subunit of (oLHbeta) ovine luteinizing hormone significantly reduced their fertility. To determine whether the major action of the vaccine was interruption of pregnancy, by suppression of "corpus luteum rescue," or inhibition of ovulation, we administered the progestational agent (MPA) medroxyprogesterone acetate from day 4 through day 40 after mating. In the untreated immunized group, the pregnancy rate was significantly below that of control monkeys. MPA treatment restored the fertility rate of immunized animals to that of the control group. These results strongly support the assumption that the antifertility action of antibodies of oLHbeta is due to prevention of corpus luteum rescue. Whether the lack of corpus luteum rescue resulted because of neutralization of rhesus monkey chorionic gonadotropin or from a defective corpus luteum, as is found in animals with short luteal phases, cannot be determined from these studies. The successful reversal of the antifertility effect, however, suggests that the circulating antibodies do not interfere with normal ovulation or with the normal development and implantation of the blastocyst.

The relative expressed estrogenicity of oral contraceptives.

PIP: Total effective estrogenicity of several human oral contraceptives was investigated through a method determining uterine weight in immature rats. The preparations, normally given to human females in tablet, form were Norinyl-1 (.05 mg mestranol, 1mg norethindrone), Norinyl-2 (.10 mg mestranol, 2 mg norethindrone), Ovulen (.10 mg mestranol, 1mg ethynodiol diacetate), Enovid-E (.10 mg mestranol, 2.5 mg norethynodrel), and Enovid-5 (.075 mg mestranol, 5mg norethynodrel). Each products was administered in total doses of .0025, .005, and .01 of a tablet. Each dose had 3 trials, approximately 10 mice to a trial. Each mouse was given the compound in .2 ml aqueous vehicle orally, daily for a 3-day period so that the sum of the daily doses equaled 1 of the tablet fractions above. Autopsy, on Day 4, discovered the ratio of mg uterus/gm body weight. A .0025 fraction of a tablet of Norinyl-1 produced a mean uterine ratio of 1.79, while control (untreated) mice had a mean ratio of 1.06. Norinyl-2, Ovulen, Enovid-5 and Enovid-E, judging from the corresponding increases in ratios from the control ratio, were found to be 2.1, 2.7, 6, and 8 times, respectively, more estrogenic than Norinyl-1. The relatively high estrogenicity of the Enovids is probably due to the conversion of norethynodrel to estrogenic compounds.^ieng