Concentration of receptors for estradiol and progesterone in canine endometrium during estrus and diestrus.

Receptors for estrogen and progesterone were measured in cytosols prepared from specimens of canine endometrium obtained at late proestrus, day 4 of estrus, day 2 of diestrus, and at 10 day intervals from days 10 through 80 of diestrus. Twenty nine adult bitches were used, with 2 to 4 dogs used at each time point. Concentrations of estradiol receptors measured in endometrial cytosols from late proestrus through day 10 of diestrus were similar (mean +/- SEM: 9.9 +/- 2.2, 10.5 +/- 1.2, 16.3 +/- 1.6, and 16.2 +/- 2.9 pmol/g of tissue at proestrus, day 4 of estrus, days 2 and 10 of diestrus, respectively). As serum concentrations of progesterone increased during early diestrus, the concentration of estradiol receptors decreased and were significantly (P less than 0.05) lower on days 30 (4.9 +/- 1.3 pmol/g of tissue) and 40 (3.7 +/- 0.6 pmol/g of tissue) of diestrus. After day 40 of diestrus, when serum concentrations of progesterone were approaching basal concentrations, the concentration of estradiol receptors increased and remained significantly (P less than 0.05) higher from days 60 to 80 of diestrus (day 60, 13.4 +/- 2.9; day 70, 15.7 +/- 1.7; day 80, 19.8 +/- 2.4 pmol/g of tissue). As observed for estrogen receptors, the concentration of endometrial receptors for progesterone also gradually increased from late proestrus (4.9 +/- 1.3 pmol/g of tissue) to day 2 of diestrus (6.4 +/- 0.3 pmol/g of tissue).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of progesterone on the oviductal epithelium in estrogen-primed prepubertal beagles: light and electron microscopic observations.

A total of 45 prepubertal beagles 6 to 8 weeks of age were used to study the cytological changes that accompany regression of the oviductal epithelium. The oviductal epithelium in untreated pups consisted of undifferentiated low cuboidal cells that measured 10.3 +/- 2.0 microns in height. In response to estradiol (E2), low cuboidal cells underwent hypertrophy, hyperplasia, and cytodifferentiation and gave rise to columnar ciliated and secretory cells. After 12 days of E2 treatment the epithelium was fully differentiated and measured 29.4 +/- 2.6 microns in height with 56% of the cells possessing cilia. When E2 treatment was continued for an additional 12 days, the epithelium was maintained in a differentiated state. However, if E2 treatment was terminated or progesterone (P) given alone or in conjunction with E2, the oviductal epithelium regressed and after 6 days was composed of low cuboidal cells that ranged in height from 9 to 14 microns with approximately 25% of the cells possessing cilia. A variety of cytological changes characterized the process of regression. The most immediate signs that regression was underway was a reduction in the height of the epithelium and the presence of cells with shrunken, pleomorphic nuclei that lacked prominent nucleoli. Degenerative events included: pinching off and shedding of the apical cytoplasm of cells comprising the epithelium, extrusion of whole cells and/or nuclei, and resorption of cilia and basal bodies. During the first 6 days following E2 withdrawal or P treatment, macrophages and cellular debris were frequently present within the lumen of the oviduct. The process of regression did not proceed synchronously throughout the ampulla of the oviduct, nor did all cells appear to degenerate in the same manner. The cytological changes that accompanied oviductal regression following P treatment were identical to those observed following E2 withdrawal. Results from experiments conducted in the present study show that: E2 induces the oviductal epithelium to differentiate and is required to maintain the epithelium in a differentiated state, E2 withdrawal or P treatment causes the oviductal epithelium to regress, at least three distinct degenerative processes are involved in the transition of columnar ciliated and secretory cells into low cuboidal cells, and regression does not occur synchronously throughout the ampulla region of the oviduct.

Hormonal regulation of cytoplasmic estrogen and progesterone receptors in the beagle uterus and oviduct.

The hormonal regulation of uterine and oviductal cytoplasmic estrogen and progesterone receptors was studied in immature beagles that were untreated, treated with estradiol-17 beta, or treated sequentially with estradiol and progesterone. Estradiol treatment increased the concentration of estrogen receptors in both tissues. Progesterone receptors were not detectable in the reproductive tract of untreated animals, but increased dramatically under the influence of estradiol. Estrogen withdrawal following estrogen stimulation concomitant estrogen plus progesterone administration, and estrogen withdrawal plus progesterone administration all caused significant reductions in both estrogen and progesterone receptors in uterine oviductal cytosols when compared to estrogen treatment alone. Estrogen withdrawal resembled estrogen plus progesterone administration in reducing both estrogen and progesterone receptor levels, although estrogen withdrawal plus progesterone administration resulted in a further reduction in both receptor concentrations. The same positive and negative relationships between estrogen and progesterone receptor content were observed in uterine cytosols from cycling and ovariectomized adults. These data suggest that estrogen and progesterone regulate their respective receptors and that tissue sensitivity to both steroids may be controlled by mechanisms involving fluctuations in receptor concentration in the reproductive tract of the beagle.

Analysis of progesterone receptor binding in the ovine uterus.

The appropriate conditions for the measurement of ovine uterine cytoplasmic progesterone receptors (PR) have been determined to be 20 nM 3H-progesterone (3H-P4) with and without a 100-fold excess of non-radioactive progesterone (P4) 0-4 degrees C and 4 h of incubation. Under these conditions PR readily exchanged bound progesterone for progesterone added during the assay. This exchange occurred even when saturating concentrations of P4 were present. The progestins, R5020 and P4, effectively competed for the ovine uterine PR binding while non-progestin steroids and diethylstilbestrol failed to compete for the PR binding. The dissociation constant (Kd) measured for the 3H-P4 binding was 1.60 x 10-9 M indicating that the 3H-P4 binding was of high affinity. The levels of PR and the dissociation constant measured using 3H-R5020 in place of 3H-P4 were similar indicating a lack of corticosteroid binding globulin (CBG)-like binding in the ovine uterus.

Steroidal control of rat uterine 17 beta-hydroxysteroid dehydrogenase activity.

The interconversion of estradiol-17 beta and estrone in the rat uterus is due to the action of 17 beta-hydroxysteroid dehydrogenase. Whole uteri or 800 x g supernatant fractions of the uteri were incubated in the presence of [3H] estradiol-17 beta and NAD at 37 degrees C for 3 h or 1 h, respectively. In the mature rat uterus the oxidation of estradiol-17 beta and estrone was dependent on the stage of the estrous cycle, suggesting hormonal control. The 17 beta-hydroxysteroid dehydrogenase activity was highest at estrus (200 fmol estrone) and lowest at diestrus (80 fmol estrone). An enhancement of activity occurred when adult rats at each stage of the estrous cycle were administered estradiol-17 beta, while progesterone administration at each stage resulted in decreased enzyme activity. The uterine 17 beta-hydroxysteroid dehydrogenase activity of estradiol-17 beta treated ovariectomized rats was time and dose dependent but decreased when progesterone was administered with or without estradiol-17 beta administration. These results suggest that estradiol-17 beta caused an increase in enzyme activity that was inhibitable by progesterone in the rat uterus. The increased 17 beta-hydroxysteroid dehydrogenase activity may reflect a specific response of the rat uterus to estradiol-17 beta.

The role of estrophilin in estrogen action.

PIP: The role of estrophilin in estrogen action was reviewed. The interaction of uterine cells with estradiol involves the association of estradiol with estrophilin followed by temperature-dependent translocation of the resulting complex to the nucleus. The steroid binding unit of estrophilin undergoes an alteration (receptor transformation) that is recognized by an increase in its sedimentation rate and by its ability to bind to isolated uterine nuclei or chromatin and to alleviate a tissue specific deficiency in the ribonuclei acid (RNA) synthesizing capacity. The estrophilin complex influence on RNA synthesis in isolated nuclei shows the same quantitative, qualitative and tissue specificity characteristics as evoked by the administration of estradiol in vivo. It was concluded that receptor transformation is an important step in estrogen action and that a major role of the hormone is to induce conversion of the native estrophilin to a biochemically functional form.^ieng

Binding proteins for an ecdysone metabolite in the crustacean hepatopancreas.

When crustacean hepatopancreas is incubated in the presence of alpha-(3)H]ecdysone of high specific activity and is then homogenized and centrifuged, a peak of protein-radioactivity is recovered after gel filtration of the 105,000 x g supernatant. Analysis of this peak by sucrose gradient centrifugation revealed the presence of two complexes of protein and labeled material ( approximately 11.5 S and 6.35 S). The same results were obtained in vivo. On standing at low ionic strength, the lighter component disappeared, suggesting that the heavier component is an aggregate of the lighter one. Chemical analysis of radioactive material in the complex revealed that it is not alpha- or beta-ecdysone nor any previously described metabolite of the ecdysones. This new metabolite of alpha-ecdysone is found mainly in the incubated hepatopancreas. Partial structures consistent with the analytical data are inferred for this metabolite. It is suggested that the metabolite may be active in the action of molting hormone.

Aspects of research on insect growth hormones.

Current research on insect growth hormones includes studies on the binding of hormones to receptor molecules, probably proteins. Evidence has been obtained that this process does in fact occur and may be the means whereby the hormones "recognize" target tissues. Other studies on the possibility of a feedback effect when growth hormones are used for insect control suggest that there is a positive feedback relationship between the hormone titre and the activity of prothoracic glands and corpora allata, but the details are not yet clear. Cyclic adenosine 3',5'-monophosphate has an important role as "second messenger" in vertebrate endocrinology and may also be important in insects. Studies have shown that adenyl cyclase is present in pupal epidermis and the preliminary results have shown that it can be stimulated by a steroid hormone.