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Recently, it has been shown that the environment contains a large variety of chemical substances possessing estrogenic activity (ecoestrogens/environmental estrogens). In this connection, the problem of estrogenic effects exerted by the environment on animal ontogenesis is very important. Here, we review that available data concerning the effects of ecoestrogens on the development of the reproductive system in mammals. We discuss issues of reproductive toxicology related to the effects of these substances during prenatal and postnatal development, with special attention to the effect of ecoestrogens and modern reproductive technologies on preimplantation embryonic development.

The dynamics of testosterone-1 alpha, 2 alpha-3H(n) intake by different tissues of genital tract was studied in the guinea pig embryos from the 23rd day of development till birth. The specific intake was noted at all developmental stages studied and in all genital tract rudiments. The Selective intake was observed in the male embryos in the genital tubercle from the 29th day, in the ducts from the 46th day and in the urogenital sinus from the 26th day. In the female embryos it was found in the genital tubercle on the 26--28th day and from the 35th, in the ducts from the 46th day and in the urogenital sinus on the 32--35th, 46--50th days and prior to birth. The specific intake was also observed in the gonads of embryos of both sexes. The data obtained suggest the presence of reception to androgen prior to the beginning of morphogenesis of the genital system and the acquisition of increase sensitivity to the hormone in the homologous rudiments during the critical periods of differentiation of organ targets by the male type.

The total protein synthesis rate in the reproductive tract and muscles of rabbit fetuses was evaluated at the 18th-22nd day of development by the intensity of 3H-leucine incorporation in experiments in vitro. Testosterone increased the total protein synthesis rate in the tissues of the reproductive tract at all the developmental stages under study. The highest rate of protein synthesis was recorded on the 18th day of development.

The time course of uptake of testosterone-1 alpha, 2 alpha-3H (n) and (4-14C)-estradiol by homologous tissue rudiments of the developing reproductive system of rabbit embryos of both sexes was studied in in-vitro experiments from the 18th till the 25th day of development. It was found that the same rudiments of the target organs of the embryos of both sexes are capable of uptaking both hormones. At the "crucial" moment of sexual differentiation (on the 21st day) the uptake of both hormones in the genital tubercle and in the urogenital sinus was greater in female embryos than in male ones. In males, the uptake of androgen was higher than that of estrogen. At the same time the uptake of testosterone-1 alpha, 2 alpha-3H(n) by the genital ducts was higher in male embryos than in female ones.

The dynamics of radioactivity in subcellular fractions of the reproductive system and muscle has been studied in the guinea pig embryos from the 21st day of development till birth after the preincubation in a medium containing 1 alpha,2 alpha-3H(n) testosterone (T-3H). The total uptake of T-3H per mg tissue is higher in the reproductive system than in the muscle and attains the highest values during the period of differentiation of target organs by the male type (30-33 days). The nucleocytoplasmic ratio of radioactivity is shifted towards its increase in the nucleus with maximum on the 41st-45th days and by the moment of birth. Radioactivity in the microsomal fraction is higher than in the cytosol (soluble proteins). From the 27th day of development on, when the hormone uptake becomes selective, the radioactivity in the cytosol from the reproductive organs is higher than in the muscle tissue. The data obtained suggest the importance of processes in microsomes for differentiation and organogenesis of reproductive system.

The rate of synthesis of cytoplasmic and nuclear proteins in the reproductive tract and muscle of rabbit embryos from 17 to 23 days of development was estimated by the intensity of 3H-leucine incorporation per 1 mg protein for 30 min in vitro. Testosterone increased several-fold the rate of synthesis of both cytoplasmic and nuclear proteins. At the same time the intensity of synthesis of nuclear proteins was several times higher that of cytoplasmic ones and attained the max values on the 20 day of development.