[Uterine estrogen sulfotransferase and estrogen sulfatase in embryo implantation]. / Estrógeno sulfotransferasa y estrógeno sulfatasa uterinas en la implantación embrionaria.

The relation conjugated/unconjugated estrogens associated with reproductive processes has brought about the interest to study the biological role and regulation of the estrogen sulfotransferase and estrogen sulfatase which participate in the formation and hydrolysis of estrogen 3-sulfates, respectively. In this paper, both activities were measured through the reciprocal conversion of 3H-estrone sulfate and 3H-unconjugated estrogen during in vitro incubation with implantation sites (SI) and non-implanted sites (SNI) from the rat uterus, during the process of embryo implantation. Contrasting enzyme activities were found in these tissues. While sulfotransferase activity was higher in SI than in SNI (0.205 vs 0.144 pmol of E1S formed/mg protein/h, the inverse was found for the sulfatase (1.470 vs 1.977 pmol of E1 formed/mg protein/h). These results indicate the presence of both enzymes in the rat uterus and suggest the existence of a mechanism in SI that locally regulate the concentration of free and sulfoconjugated estrogens in which these enzymes participate.

[Estrogenic sulfuration and desulfuration processes and their significance in breast carcinoma]. / Procesos de sulfatación y desulfatación estrogénica y su importancia en el carcinoma mamario.

Estrogen conjugates are generally considered as inactivated forms devoid of any estrogenic activity. In some therapies, such as that used during menopause, high dose of estrogen sulfate are currently used as non estrogenic agent. However, precaution should be taken since a considerable amount of this conjugate can be converted into estradiol-17 beta (E2), the most biologically active hormone. In vitro, estrone sulfate (E1S), is converted into estrone (E1) and E2 by the action of estrogen sulfatase and 17 beta-oxydoreductase enzymes. Since the half life E1S in plasma is much higher than that of other estrogens, this conjugate could provide a continuous supply of E2 to estrogen target cells, which may be biologically important. It is the purpose of this review to point out the important role of estrogen sulfates in breast carcinoma.

[Hormonal requirements for blastocyst implantation]. / Requerimientos hormonales para la implantación del blastocisto.

In the early stages of pregnancy, embryo development and preparation of the endometrium must be synchronized in a very precise manner, in order to let blastocyst establishment. This state results from the interactions of steroid hormones, progesterone and/or estrogens. The hormonal requirements for embryo implantation vary considerably among different mammals. Systemic progesterone intervention is common to the various species; however, the requirement for ovarian estrogen seems not to be. In this paper, certain new aspects of the hormonal requirements for blastocyst implantation are reviewed.

[Endocrine capacity of the mammalian blastocyst. I. Biosynthesis and metabolism of progesterone]. / Capacidad endocrina del blastocisto de mamífero. I. Biosíntesis y metabolismo de progesterona.

In order that blastocyst implantation occurs in mammals, it is required the synthesis and secretion of several substances including steroid hormones by the preimplanted embryo. In this paper, we analyze the embryo endocrine capacity for biosynthesis and secretion of progesterone and several progestines.

[Endocrine capacity of blastocysts in mammals. I. Progesterone biosynthesis and metabolism]. / Capacidad endocrina del blastocisto de mamífero. I. Biosíntesis y metabolismo de progesterona.

In order that blastocyst implantation occurs in mammals, it is required the synthesis and secretion of several substances including steroid hormones by the preimplanted embryo. In this paper, we analyze the embryo endocrine capacity for biosynthesis and secretion of progesterone and several progestines.

[Influence of tubal and uterine milieu in the embryonic development]. / Influencia del medio tubario y uterino en el desarrollo embrionario.

Establishment of pregnancy in mammals is a process resulting of closely concerted events. The participation of the embryo through its development and secretory activity on the one hand, and on the other, the oviductal and endometrial tissues, by means of their secretions, give the optimal conditions to let the embryo establish creating a proper milieu for its nutrition and development. In this review, we analyze the influence of the oviductal and uterine secretions upon early embryonic development and differentiation and some transport systems of nutritional elements required in the early stages of the blastogenesis.