geoscience.net logo
+ Resolve Article
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter

+ Translate
+ Subscribe to Site Feed
GeoScience Most Shared ContentMost Shared Content

Anti-implantation activity of antiestrogens and mifepristone


, : Anti-implantation activity of antiestrogens and mifepristone. Contraception. 54(4): 253-258

To develop a better postcoital contraceptive, the following antiestrogens were tested for their anti-implantation activity in the rat: anordrin, anordiol, tamoxifen, ICI 182,780, and RU 39411. The compounds were administered orally or subcutaneously (sc) to female rats on days 1, 2, and 3 of pregnancy. All the antiestrogens tested were 100% effective in preventing blastocyst implantation. The lowest effective doses when administered orally were 10, 1.25, 0.062, 6.0 (partially effective), and 0.01 mg/kg/day, respectively. The estimated median effective doses (ED-50) were 5.60, 0.40, 0.035, 5.40, and 0.0074 mg/kg/day, respectively. When administered sc, the minimum effective doses in preventing blastocyst implantation in all animals were 2.0, 0.1, 0.1, 0.1, and 0.01 mg/kg/day, respectively. Anordrin, anordiol, and ICI 182,780 were more potent when administered sc; whereas tamoxifen and R U 39411 were effective at similar doses when administered parenterally or orally. RU 39411 was the most potent among the antiestrogens tested and should be evaluated as a potential postcoital contraceptive. The administration of mifepristone, an antiprogestin, at a dose of 8 mg/kg/day blocked blastocyst implantation in all treated animals; whereas at a dose of 4 mg/kg/day or lower, the drug was ineffective. These findings confirm that estradiol and progesterone are essential for blastocyst implantation in the rat. The capacity of mifepristone to potentiate the anti-implantation activity of the antiestrogens was also determined. The combination of a noneffective dose of each of the antiestrogens (anordrin, anordiol, and tamoxifen), and RU39411, with mifepristone at a non-effective dose, prevented pregnancy, demonstrating that an antiprogestin and antiestrogen act synergistically in blocking blastocyst implantation in the rat. The antiestrogen compounds whose anti-implantation activities were potentiated by mifepristone were found to possess significant estrogenic activity, when assayed by measuring the increase in the uterine weights of ovariectomized rats. The only exception was ICI 182,780, which showed no estrogenic activity in the uterine weight bioassay and did not act synergistically with mifepristone in blocking blastocyst implantation. Estradiol was effective in preventing pregnancy at a dose of 1 mu-g/kg/day. The combination of non-effective doses of estradiol and mifepristone did not prevent pregnancy. The findings that mifepristone potentiates the anti-implantation activity of those antiestrogens with intrinsic agonist activity suggests that the synergistic effect may be a unique property of this class of antiestrogens.

US$19.90

PMID: 8922879

DOI: 10.1016/s0010-7824(96)00196-5


Other references

Zimmerman, L.N., 1957: Colonial differentiation between Escherichia coli B and Escherichia coli B/r. Nature 180(4596): 1217-1218

Dahse, G., 1980: The physician malpractice process, causes and proof. Beitrage Zur Gerichtlichen Medizin 38: 9-12

Szunics, L., 1969: Data on the physiological specialization of E. g. f.sp. tritici. Among 17 races isolated race 16 (22.98%) predominated, followed by 18 (14.76%) and 19 (13.12%). Race 34 (4.92%) from some new promising wheat vars, was the most virulent. The var. Bezostaya 1 was susceptible to all the races.

Bailo E.T.hir; Schandelmeier Heinz, 1999: Keraf petrotectonic assemblage NE Sudan; petrological and geochemical signatures of the passive margin-related sediments on the eastern foreland of the Nile Craton. The Neoproterozoic lithologies which separate the juvenile ensimatic Arabian-Nubian Shield from the, isotopically distinguished, older ensialic crust (Nile Craton) are characterised by unique structural and tectonic setting, textural & mineralogic...

You, Y.H.; Li, C.; Pfeifer, G.P., 1999: Involvement of 5-methylcytosine in sunlight-induced mutagenesis. In human skin cancers, more than 30 % of all mutations in the p53 gene are transitions at dipyrimidines within the sequence context CpG, i.e. 5'-TCG and 5'-CCG, found at several mutational hotspots. Since CpGs are methylated along the p5...

Batistella, C.; Moraes, E.; Maciel-Filho, R.M.ciel, M., 2002: Molecular distillation process for recovering biodiesel and carotenoids from palm oil. Carotenoids and biodiesel from palm oil were recovered through a process involving neutralization and transesterification of palm oil followed by molecular distillation of the esters. The concentrated obtained contains more than 30,000 ppm of caro...

Salatic D.; Deusic S., 1978: Separation of the boehmite along with kaolinite by flotation. [Papers] - International Congress for the Study of Bauxites, Alumina and Aluminum

Anonymous, 1957: Handling minnows in perforated plastic bags. Minnows 2-3.5 in. long were placed in 8 x 15 inch plastic bags closed with rubber bands and permitted to drift at random in holding tanks and small ponds. The fish were held for 2 hours with no artificial aeration and without apparent stress.

Lau, S.; Böhm, C.; Volbert, R., 2007: Mental disorder and competence to testify. The article describes the approach used in the psychiatric assessment of a person's competence to testify and discusses different disorders. Psychiatrists are often asked to comment on the competence to give evidence if witnesses' behavi...

Ellerbroek, U., 1968: The Hamburg polyclinic for diseases of the limbs. Phlebologie 21(1): 15-18