Effect of Anordrin on serum levels of sex hormone binding globulin, caeruloplasmin and ovarian function

Effect of anordrin on the development of mouse preimplantation embryos in vitro

PURPOSE

The in vitro effect of anordrin and anordiol on the development of mouse two-cell embryos was studied.

METHOD

Female mice were primed with gonadotropins for superovulation and caged with male mice. Preimplantation embryos, at the two-cell stage, were recovered from the oviducts at 40 hr post-hCG. In the first experiment, two-cell embryos were exposed to culture medium containing different concentrations of anordrin for 3, 12, 24, and 80 hr and then grown in the anordrin-free culture medium and assessed for the formation of total and hatching blastocysts at 80 hr. In the second experiment, two-cell embryos were grown in culture medium containing different concentrations of anordiol and assessed for the formation of total and hatching blastocysts at 80 hr in vitro.

RESULTS

Exposure of two-cell embryos to anordrin concentrations of 2.5-7.5 micrograms/ml for 12 hr, 2.5-5.0 micrograms/ml for 24 hr, and 2.5 micrograms/ml for 80 hr caused significant inhibition of the formation of total blastocysts and to 2.5-7.5 micrograms/ml for 12 hr, 1.0-2.5 micrograms/ml for 24 hr, and 1.0 micrograms/ml for 80 hr caused significant inhibition of the formation of hatching blastocysts, in a exposure time-dependent and dose-dependent manner. Exposure of two-cell embryos to anordiol concentrations of 15-25 micrograms/ml for 80 hr caused significant inhibition of the formation of total blastocysts and to 15-20 micrograms/ml for 80 hr caused significant inhibition of the formation of hatching blastocysts in a dose-dependent manner.

CONCLUSION

Anordrin and its metabolite anordiol inhibit the development of two-cell embryos in vitro.

Anordiol is more potent than anordrin for terminating pregnancy when administered with RU 486

In view of the unexpected ability of anordrin to synergize with RU 486 in terminating pregnancy, it was pertinent to examine the actions of the dihydroxylated metabolite of anordrin, anordiol, alone and in combination with RU 486. Does of RU 486 (1 mg/kg/day) and anordiol (0.6 mg/kg/day) that were ineffective when given alone terminated pregnancy with complete resorption of embryos when administered together. A smaller dose of anordiol than anordrin is required to achieve this synergistic effect with RU 486. This anordrin metabolite increased uterine weight in the ovariectomized rat similar to estradiol. The estrogenicity of anordiol in the uterine weight assay was about 1/120 of that of estradiol. Anordiol does not exert antiestrogenic activity in the uterine weight assay when administered at doses that terminate pregnancy. Administration of anordiol at doses that do not terminate pregnancy resulted in a significant suppression of serum progesterone concentrations during the period of medication; these observations suggest that anordiol has an inhibitory effect on progesterone biosynthesis. When the same dose of anordiol was given concomitantly with sufficient RU 486 (e.g., 1 mg/kg/day) to terminate pregnancy, the progesterone levels were reduced to low levels throughout the experiment. These observations support the postulate that the actions of anordrin are mediated by its metabolite, anordiol. The administration of anordiol plus RU 486 results in a more dramatic change in the functional progesterone:estradiol ratio than when either agent is administered alone.

Termination of early pregnancy in the rat, rabbit, and hamster with RU 486 and anordrin

The effectiveness of oral RU 486 and anordrin given alone and in combination for terminating early pregnancy was tested in the rat, rabbit, and hamster. In the rat and rabbit, the combination of RU 486 and anordrin is more effective in terminating pregnancy than either of the two compounds used alone. A non-effective dose of RU 486 combined with a non-effective or a sub-effective dose of anordrin, or a low effective dose of RU 486 in combination with a non-effective dose of anordrin, exerted additive or synergistic effects resulting in resorption of embryos and termination of pregnancy in rats and rabbits. The serum progesterone as well as estradiol concentrations were significantly suppressed by these combinations when pregnancy was terminated. In the hamster, however, RU 486 was not effective in interrupting early pregnancy, even at a 4-fold higher dose than was effective in the rat, due to the fact that RU 486 does not bind to the progestin receptor in this species. Unexpectedly, there were also no effects of anordrin on pregnancy termination in the hamster even at high doses. It is concluded that in rat and rabbit, the synergistic action between RU 486 and anordrin not only greatly enhances efficacy in terminating pregnancy but also reduces substantially the doses required to produce this effect.

Additive effect of RU 486 and anordrin on pregnancy interruption in the mouse

The effect of various doses of anordrin and RU 486, alone or combined, on serum progesterone (P) levels, fetal resorption, and recovery of ovulation was studied in mice. Each drug was given as a single sc injection on day 7 of pregnancy and autopsy was performed on days 8, 9, or 11. Serum P was normal at 24 h but fell significantly 48 h after treatment with anordrin (0.05 mg). Doses of 0.05 or 0.2 mg anordrin were effective in interrupting pregnancy in 30% and 70% of pregnant mice, respectively. RU 486, 0.01 mg per mouse, induced a pronounced decrease of P levels 24 h after treatment and interrupted pregnancy in 50% of pregnant mice. The combined treatment with submaximal doses of anordrin plus RU 486 did not further decrease P levels, but increased the proportion of mice with fetal resorptions to 90%. The combination of small doses of anordrin with RU 486 had an additive effect on pregnancy termination. The additive effect required a dose of RU 486 above the threshold level. Direct observation of aborted fetuses indicated that the resorptive process occurred earlier with RU 486 than with anordrin. Recovery of ovulation was associated with pregnancy termination in a high proportion of mice treated with either drug or their combination.