The effects of sex-steroids on the synthesis of uterine non-histone proteins

Effect of estradiol and progesterone on phosphatidylinositol metabolism in the uterine epithelium of the mouse

The effect of estradiol and progesterone on uterine phosphatidylinositol (PtdIns) metabolism was examined in whole uteri and separated uterine luminal epithelium of ovariectomized mice. Incorporation of [3H]myo-inositol in vitro, into inositol-containing phospholipids extracted from whole uteri, increased in mice injected with estradiol, with maximal incorporation at 9-12 h. The breakdown of PtdIns to inositol polyphosphates was also stimulated in whole uteri by estrogen, with an abrupt increase between 6 and 9 h. Comparable increases in both processes occurred in the uterine epithelium after estrogen stimulation and were inhibited by progesterone pretreatment which by itself had little or no effect. These results suggest that PtdIns metabolism is involved in the stimulation of uterine epithelial cell proliferation by estrogens, and its inhibition by progesterone.

Effects of female sex hormones on lipid metabolism in the uterine epithelium of the mouse

1. The effects of oestrogen and progesterone on synthesis and composition of lipids in the uterine epithelium were studied. 2. Oestrogen treatment for up to 18 hr resulted in an increased incorporation of [14C]acetate into all classes of lipids, but particularly into cholesterol. 3. Progesterone treatment increased incorporation into all classes of lipids except cholesterol and completely inhibited the oestrogen-induced incorporation into cholesterol. We suggest that this may be the mechanism whereby progesterone blocks uterine epithelial cell proliferation. 4. Oestrogen increased incorporation into all classes of phospholipids, and progesterone pretreatment inhibited the marked oestrogen-induced incorporation into phosphatidylinositol. 5. Both oestrogen and progesterone, but particularly progesterone, increased the epithelial cell phospholipid to cholesterol ratio. 6. Oestrogen induced changes in epithelial phospholipid fatty acyl composition: particularly marked was a time related reduction in 20:4 which was inhibited by progesterone pretreatment to only a minor degree.

Cell growth and cell proliferation may be dissociated in the mouse uterine luminal epithelium treated with female sex steroids

The mouse uterine epithelium under various hormonal regimes is a good system to identify biochemical events associated with cell growth, DNA synthesis and cell division. This is because estradiol-17 beta stimulates the cells to undergo a synchronized wave of DNA synthesis and cell division. Estriol, on the other hand, also stimulates DNA synthesis but because of the rapid loss of this hormone from the tissue some of the cells abort, giving a constant epithelial cell number. Three days of progesterone pretreatment, however, completely suppresses the estradiol-17 beta-induced wave of DNA synthesis and cell proliferation. Using these hormonal treatments we have shown that both estradiol-17 beta and estriol stimulate protein and rRNA synthesis with the concomitant increase of protein and rRNA per mg of DNA. These macromolecules accumulated in direct proportion to the fraction of cell committed to DNA synthesis. Estriol, however, did not sustain the growth responses and at the peak of DNA synthesis both rRNA and protein synthesis had returned to control levels. Progesterone pretreatment, despite inhibiting the proliferative response, failed to inhibit any of the estradiol-17 beta-induced increases in protein and rRNA synthesis. Indeed 12 h after estradiol-17 beta injection the cells had identical protein and rRNA contents, regardless of whether they had been exposed to progesterone or not. The present data therefore suggests that in the uterine epithelium cell growth as defined by protein and rRNA accumulation and DNA synthesis represents two independently regulated pathways.

The effects of sequential administration of 17 beta-estradiol on the synthesis and secretion of specific proteins in the immature rat uterus

We report here results of a study of the effect of sequential administration of 1 microgram 17 beta-estradiol in vivo on the incorporation of L-[35S]methionine into specific proteins in vitro in the immature rat uterus. One-dimensional SDS-PAGE analysis of labeled secreted uterine proteins and cellular proteins extracted from the luminal epithelial and from the stroma plus myometrial uterine fractions revealed that estradiol preferentially stimulated the synthesis of 110 K, 74 K and 66 K secreted proteins, 180 K and 110 K epithelial proteins and a 175 K stroma-myometrial protein among others, while it decreased the relative rate of synthesis of a 32.5 K secreted protein and a 70 K stroma-myometrial protein. The 110 K protein, a secreted luminal epithelial protein whose labeling in vitro dramatically increased greater than 60-fold per mg endometrial DNA after in vivo estrogen stimulation, may be a useful marker for studying estrogen action in the luminal epithelium of the immature rat uterus. Comparison of the secreted proteins labeled at 28 h (4 h after a second injection) and at 54 h (6 h after a third injection) revealed that estradiol effected a sequential change in the pattern of synthesis of secreted uterine proteins in vitro. Comparison of the number and magnitude of changes in the synthesis of specific proteins in the luminal epithelium and the stroma plus myometrium revealed that protein synthesis in the luminal epithelium is clearly more responsive to estradiol and readily distinguishable from the responsiveness of the stroma plus myometrium.

Effects of progesterone on uptake and metabolism of 17 beta-estradiol by mouse uterine luminal epithelium

The influence of progesterone (P4) pretreatment on the uptake and retention of [3H]estradiol-17 beta ([3H]E2) in whole uterus and luminal epithelium was examined in ovariectomized mice. After s.c. injection of 50 ng [3H]E2 uterine, epithelial and epithelial nuclear levels of radioactivity were maximal 3 h post-injection: maximum epithelial levels were sustained from 3 to 6 h in Pa-treated, but not control tissue. P4 treatment did not significantly alter the proportion of epithelial or uterine radioactivity recovered as [3H]E2, or the intracellular distribution of the hormone. Preparation of epithelial suspensions in buffer containing excess 17 beta-estradiol (E2) did not significantly alter their [3H]E2 content. After intraluminal injection of 100 pg [3H]E2 rates of loss from uterine, epithelial and epithelial nuclear preparations did not differ significantly between control and P4-treated tissues. We conclude that P4 does not inhibit E2-induced luminal epithelial mitosis by preventing E2 reaching the epithelial cells and nuclei, by changing its distribution in the tissue, or by increasing its rate of loss from the tissue or its metabolism to less active estrogens like estrone.

Uterine proteins influenced by estrogen exposure. Analysis by two-dimensional gel electrophoresis

Two-dimensional gel electrophoresis has been utilized as a technique to investigate uterine protein patterns and protein distribution after estrogen administration. A combined in vivo stimulation, in vitro labeling technique was devised to investigate these questions. Animals were first primed in vivo with estrogen for 2 h to activate the normal early response to hormone and to stimulate protein synthesis. Tissue was removed and protein labeling occurred for 4 h with [35S]methionine. Tissue was then re-exposed in vitro to either estrogen or saline for an additional 1 h. Subfractionation of the uterine tissue and analysis of labeled proteins by two-dimensional gel electrophoresis has indicated the disappearance of some proteins from the cytoplasmic compartment and the appearance of other proteins in the nuclear fraction of estrogen-exposed samples. These findings suggest that in the mouse uterus, estrogen influences protein synthesis and also a redistribution of these proteins into various cellular fractions where they may act to elicit estrogen action.