In vivo response of secretory component in the rat uterus to antigen, IFN-gamma, and estradiol

Intrauterine immunization of ovariectomized rats with SRBC is known to elicit pronounced IgA and IgG antibody responses in uterine secretions of immunized uteri. To determine whether secretory component (SC), the receptor for transporting polymeric IgA from tissues to mucosal surfaces, was also influenced by Ag, ovariectomized rats were immunized and boosted by placing SRBC into the lumena of individual uterine horns. In response to Ag, the levels of polymeric IgA, as well as free SC and SC bound to polymeric IgA, increased in uterine secretions. When ovariectomized animals were treated with estradiol, a fivefold increase in SC levels was observed in the immunized horns, indicating that a hormone response is superimposed on the Ag-induced stimulation of uterine SC. To determine whether IFN-gamma influences the presence of SC in uterine secretions, IFN-gamma was placed in the uterine lumena of ovariectomized nonimmunized rats. When uterine secretions were analyzed, significantly higher levels of SC were found in IFN-gamma-exposed uteri than were present in saline treated control animals. In contrast, intrauterine instillation of IFN-gamma had no effect on the levels of IgA in uterine secretions. This response was specific for IFN-gamma in that IFN-alpha/beta had no effect on uterine SC or IgA levels. These results indicate that intrauterine instillation of Ag, in addition to evoking pronounced antibody responses, stimulates the production of SC, which may be responsible for the transport of polymeric IgA from tissue to uterine secretions. Furthermore, they indicate that IFN-gamma placed in the uterine lumen stimulates SC production and suggest that the uterine SC response to Ag may be mediated by the action of IFN-gamma on uterine epithelial cells.     

On the regulation and turnover of progesterone metabolites in rat uterus

Recently the in vitro progesterone metabolism was shown to be inhibited in uterine tissue by association of the hormone with binding components. However, a dissociation of progesterone would impair the protection of the steroid hormone caused by complex formation. In order to study this effect, the influence of time was investigated on the metabolism of progesterone. Progesterone metabolites were analysed quantitatively from the recovered material of uteri and nutrient media by thin layer chromatography (TLC) at various time invervals. After finishing the incubation with the labelled steroid, the amount of progesterone metabolites produced increased continuously in the tissue during the following hour when the uteri were kept in nutrient medium. This indicated that the dissociation of progesterone from a hormone protein complex led to the subsequent metabolism of the unbound hormone. However, the metabolism was reduced markedly by an increase of the protein content in uterine tissue and with it by an increase of progesterone binding proteins in uterine cytosol as determined by charcoal adsorption technique. Additionally, the amount of progesterone metabolites was found to be much higher in uterine tissue than that released into nutrient medium during the time interval studied. Therefore, uterine tissue concentrates progesterone metabolites, and a rapid turnover of these substances does not occur.     

The apparent in vivo affinity of estradiol binding sites in the uterus varies during the estrous cycle of the rat

An estradiol-exchange assay system was used to determine the amounts of different estradiol receptors in the uterus of rats exhibiting a regular, four day estrous cycle. The total number of all receptors increased from a low at estrus and metestrus to a high at proestrus, before falling sharply between proestrus and estrus. These variations have been explained by alterations in the amounts of estradiol and progesterone in the serum. Similar variations were observed in the classes of free and occupied receptors; the latter varied more dramatically than the former. The changes in the amounts of free and occupied receptors could be explained by variations both in the estradiol levels in the serum and in the total number of receptors in the uterus. However, the amount of occupied receptors did not increase as much from diestrus to proestrus as expected from the increase in the estradiol levels in the serum, indicating that the apparent in vivo affinity of the receptors for estradiol was greater at diestrus than at proestrus. This difference could not be explained in terms of (i) receptor stability during the exchange assay, or (ii) of estradiol retention capacity of the serum, or (iii) of limited uptake of estradiol into the uterine cell. It is concluded that some differences must exist in the function or structure of the receptors at diestrus and proestrus.     

Multistage functional system amplifying and spreading the effect of estradiol in rat uterus

Summary Estradiol is demonstrated to induce histidine decarboxylase, and histamine is shown to activate adenylate cyclase in rat uterus. Histamine and cyclic 3,5-AMP mimic the effects of estradiol in that they enhance RNA synthesis, induce glycolytic enzymes and uterus imbibition. The data suggest that estradiol enhances by induction of histidine decarboxylase the formation of histamine, the latter activates adenylate cyclase providing accumulation of cyclic 3,5-AMP, which, probably, induces glycolytic enzymes through phosphorylation of chromatin proteins, and mediates other estradiol effects. The chain of successively acting enzymes and mediators constitutes, obviously, a cascade amplifying estradiol action. Since histamine is known to act as an intercellular mediator, attempts were made to find out the distribution of estradiol histamine and cyclic 3,5-AMP among uterus cells. Autoradiography has shown that [³H]-estradiol is bound by the nuclei of myometrium cells, [³H]-histamine was found above the cytoplasm of these cells, [³H]-cyclic 3,5-AMP is selectively bound by the cells of capillary endothelium of the uterus. The estradiol mediators seem to spread effect of hormone on cells of different types which form together a kind of multicellular functional system.     

The nuclear binding of estradiol stimulates ribonucleoprotein transport in the rat uterus

An inverse relationship exists in the rat uterus between the endogenous estradiol concentration and the rate of accumulation within the nuclei of ribonucleoproteins (RNP) that bind estradiol. Exposure of the uterine nuclei to physiological concentrations of estradiol, either in vivo or in vitro, results in the hormone binding to the nuclear RNP and the transport of the RNP-estradiol complex from the nuclei. Evidences suggest that the RNP-estradiol complex, thus released upon in vivo exposure of the nuclei to estradiol, associates with the ribosomes forming polysomes. The polysome profiles show that the hormone-binding activity is mainly associated with the rapidly sedimenting polysomal fractions.     

Cordycepin and early effects of estradiol on the immature rat uterus.

Estradiol induces the synthesis of a specific protein fraction (IP) in the uterus of the immature rat. The injection of cordycepin (3' deoxyadenosine), an inhibitor of poly A synthesis, inhibits the synthesis of IP. This fact suggests that one of the earliest effects of estrogen is the production of Hn-RNA poly-A relative to IP. Moreover, using electron microscopy, the stimulation by estradiol of the nucleolus of the immature rat uterine epithelium has been shown. Cordycepin does not affect this stimulation to any appreciable extent. Biochemical studies (incorporation of radioactive stracers into NRA, affinity chromatography on poly U-Sepharose) carried out in parallel with and under conditions comparable to those used in electron microscopy show that cordycepin does not greatly affect the increase in ribosomal RNA observed under the effect of estradiol. The blocking of IP by cordycepin and the lack of inhibition at the nucleolus level under the same conditions, show that the two early effects of the action of estrogen on the immature rat uterus are not directly correlated.     

Neurotensin enhances estradiol induced DNA synthesis in immature rat uterus

Systemic administration of Neurotensin, a tridecapeptide, in immature rats treated with estradiol benzoate significantly enhances uterine DNA synthesis as reflected by the incorporation of 3H-thymidine. The peptide may have a direct action on the uterus. Substance P, a related peptide, had no effect on uterine DNA synthesis.     

Multiphasic regulatory system mediating the effect of estradiol in rat uterus]

Estradiol is shown to induce histidine decarboxylase and histamine to activate adenylate cyclase in the rat uterus. Cyclic AMP like histamine simulates the effect of estradiol, intensifying RNA synthesis and inducing glycolytic enzymes and uterus inhibition. It was found by autoradiography that 3H-estradiol is accepted by the nuclei of some myometrium cells, 3H-histamine by their cytoplasm and 3H-cAMP is selectively bound by endothelium cells of the uterus capillaries. The estradiol messengers (histamine and cAMP) seem to mediate hormonal effect of some uterus heterofunctional cells forming a kind of multicellular functional system.     

Effect of lanthanum on the turnover of calcium in rat uterus.

Previous investigations suggest that lanthanum might enter uterine smooth muscle cells and work as intracellular calcium displacing agent. The present investigation had been carried out in order to confirm if lanthanum develops an intracellular effect. Experiments show that lanthanum brings about a marked increase of the intracellular calcium; the comparison of the uptake and of the wash-out curve of 45Ca shows that lanthanum induces a lowering of the rapid phase of 45Ca release from rat uterus, while the uptake of the labelled ion is not modified or is even enhanced. The present data demonstrate that the action of lanthanum in rat uterus is limited to the cell membrane, whose calcium extruding properties are inhibited.     

The effect of estradiol on collagen structure and organization in the immature rat uterus

An examination of collagen ultrastructure in the lamina propria of the immature ovariectomized rat uterus revealed that a single injection of estradiol (40 micrograms/kg) produced a biphasic effect on collagen structure and organization. In saline-treated animals (controls) dense populations of collagen bundles were seen throughout the extracellular matrix (EX). Cross-sections of these bundles suggested that the bundles run parallel to the long axis of the uterus and thin filaments seemed to form cross-links between collagen fibers. In contrast, large clear spaces, collagen fragments, and loosely packed bundles of collagen were observed in the EX of animals injected with estradiol 24 hr earlier. In a time course study (0, 1, 2, 4, 24, and 48 hr), estradiol treatment altered collagen structure and organization 1 hr following administration. Collagen bundles did not appear to be as densely packed as in control tissues and large clear spaces were evident in the EX. Two hours following estrogen administration, collagen fibers appeared to be fragmented and seemed to be separating from the plasma membrane of stromal cells. Four hours following estrogen administration, large clear spaces occupied most of the EX in the lamina propria. Collagen fragments were diffusely distributed throughout the EX and small cross-sectional patches of collagen bundles were present. In 48-hr-treated animals, collagen bundles reappeared and were often closely associated with the plasma membrane of stromal cells. The collagen was not as abundant as in control animals. An overview of the cellular organization of the lamina propria revealed that stromal cells in control tissues were more densely packed than in estradiol-treated tissues (4, 24, and 48 hr) and the stromal cell size appeared to increase in hormone-treated tissues. These responses provide a good model system to study the role of estradiol in the control of collagen structure and organization in the uterus.