Endometrium Of Ovariectomized Rats Research Articles

Activin βA subunit, follistatin and follistatin-like 3 are expressed in the endometrium of ovariectomized rats and regulated by estrogen replacement

Activin A is a growth factor expressed in the endometrium, where it modulates tissue remodeling and enhances decidualization. The effects of activin A are counteracted by two binding proteins, namely follistatin and follistatin-like 3 (FSTL3). We have evaluated the effects of estrogen and progestin on the endometrial expression of activin betaA subunit, follistatin and FSTL3 in ovariectomized rats. Adult female Wistar rats (n = 21) were ovariectomized and received one week later a single dose of estradiol benzoate (1.5 mg/kg body weight, i.m. injection), either alone (n = 7) or associated with depot medroxyprogesterone acetate (3 mg/kg body weight, i.m. injection, n = 7), or oil vehicle (control group, n = 7). One week later, activin betaA subunit mRNA levels had increased significantly in the uteri of rats treated with estradiol alone (7.4 fold increase over controls, P < 0.05) and to the same extent in rats receiving estradiol plus medroxyprogesterone (6.1 fold increase over controls, P < 0.05). This was accompanied by increase of betaA subunit immunostaining in estradiol and estroprogestin treated rats, which was noted only in the surface endometrial epithelium. Follistatin mRNA expression, conversely, showed a significant decrease in the groups treated with estrogen alone and estrogen plus progestin (P < 0.05), and follistatin immunostaining in the glandular epithelium was weaker in estradiol and estroprogestin-treated rats compared to controls. FSTL3 expression was similar in the 3 groups. In conclusion, the expression of activin betaA subunit increases and that of follistatin decreases following estrogen replacement in the endometrium of ovariectomized rats, and these effects are not further altered by the addition of progestin.

045 The morphological aspect of experimental endometrial implants and endometrium of ovariectomized rats treated with ovarian steroids

045 The morphological aspect of experimental endometrial implants and endometrium of ovariectomized rats treated with ovarian steroids

Cell type-specific induction of cyclin D and cyclin-dependent kinase inhibitor p27 kip1 expression by estrogen in rat endometrium

Cyclins, cyclin-dependent kinases (CDKs) and the CDK inhibitor p27 kip1 are known to be involved in the regulation of G 1/S phase transition by estrogen in the rodent endometrium. Little is known, however, of the cell-specific location and regulation of these proteins during this process, or the way they mediate the differential effect of estrogen in the epithelium and stroma of the endometrium. Here we studied the cell-specific regulation of D-type cyclin (D 1–3), of cyclin A and E, of CDK 2 and p27 kip1 by 17β-estradiol in the endometrium of ovariectomized rats. Time-course changes in these proteins in the endometrium of ovariectomized rats were examined by immunohistochemistry at 2, 4, 8, 12, 20, 28 and 32 h after estrogen stimulation. The expression of proliferation cell nuclear antigen (PCNA) was also studied as a marker of proliferating cells. As expected from previous studies, all the proteins investigated were up-regulated by estrogen, with peak times from 8 to 32 h. The induction of cyclin D 1 is predominant in the glandular epithelium, whereas cyclin D 3 increases mainly in the luminal epithelium. The up-regulation of p27 kip1 is restricted to stromal cells with a ‘gradient-like’ expression pattern, in which the sub-epithelial (functional) layer showed stronger staining than the basal layer. The differential regulation of cyclins and p27 kip1 in the epithelium and stroma of the endometrium appear indicative of distinct actions of estrogen in different cell types in the uterus, as D-type cyclins mediate the proliferative effect of estrogen in epithelial cells while p27 kip1 might help prevent the same effect in the stroma.

Benzo(a)pyrene-induced early cytopathologic changes and peroxidase activity in the endometrium of ovariectomized rats

The present study was designed to investigate whether benzo(a)pyrene (BP) alone would have cytopathologic effects on the endometrium of ovariectomized rats, and whether DES can modulate or facilitate this cytopathology. The morphology and cytochemically detectable peroxidase activity in the endometrial epithelium of castrated rats were studied 24 hr after sc administration of three to six doses on consecutive days (one dose per day) either of corn oil, BP (50 mg/kg/day), DES (20 μg/kg/day), or a combination of the latter two agents. BP alone induced mitosis, peroxidase activity, and focal squamous cell metaplasia in the endometrial epithelium of castrated rats. Peroxidase activity was weak in the granular endoplasmic reticulum of the normal epithelial cells after three and six doses of BP. However, in the focal metaplasia, the superficial squamous cells contained strong peroxidase activity after six consecutive daily doses of BP. The focal metaplasia present only after six doses of BP consisted of three to four layers of squamous cells and one to two layers of basal cells. DES-treated animals showed no formation of metaplasia or structural alterations in the epithelium, but intense peroxidase activity was present in epithelial cells after three or six daily doses. The castrates treated with three or six combined doses of BP and DES showed significant ultrastructural changes in the epithelial cells. Vacuolization of the cisternae of the granular endoplasmic reticulum was observed in the epithelial cells after three doses of BP-DES. Distinct dilation and degranulation of the granular endoplasmic reticulum as well as enlargement of mitochondria were found in all the epithelial cells of the pseudostratified hyperplastic epithelium after six consecutive daily doses of the combination, BP-DES. These ultrastructural aberrations are clearly indicative of a cytotoxic effect of BP on the endometrial epithelial cells. Collectively these findings suggest that sc administration of BP induces peroxidase activity which may lead indirectly to lesions in the endometrium of ovariectomized rats, and DES may enhance the cytotoxicity of BP by a similar mechanism.

A quantitative test for oestrogenic activity using rat endometrium lactate dehydrogenase.

In ovariectomized rats treatment with ethinyloestradiol (EOe) po started 1 week after castration and given for 4 days resulted in an increase of endometrial lactate dehydrogenase per DNA (LDH/DNA). The lambda of the dose-response curve was 0.178. In subsequent experiments EOe was used as a standard and the oestrogenic activity of four steroids given po was compared. The effect of testosterone was studied using oestradiol as a standard. If the activity of EOe is 1, the relative oestrogenic potencies of oestriol succinate, oestradiol decanoate, 11 beta-methyoxymethyl-17 alpha-ethinyl-delta 1,3,5(10)-oestratriene-3,17 beta-diol and 11 beta-methoxymethyl-delta 1,3,5(10)-oestratriene-3,16 alpha,17 beta-triol were 0.074, 0.7, 12.5 and 32, respectively. The results of the test were compared with the relative potencies of these four compounds in two biological tests, viz. the vaginal cornification in ovariectomized adult rats and stimulation of the uterine growth in immature intact rats. The relative oestrogenic potencies as measured by an increase in the endometrial LDH/DNA were in better agreement with those found in the vaginal cornification assay than with those in the uterine growth stimulation test. Testosterone caused no significant changes of LDH/DNA. We conclude that the increase in LDH/DNA in the endometrium of ovariectomized rats can be used as a quantitative assay for oestrogenic potency.

Glycosyltransferase and UDP-galactose pyrophosphatase activities in the endometrium during oestrous cycle of the rat.

UDP-galactose: glycoprotein galactosyltransferase, CMP-sialic acid: glycoprotein sialyltransferase and UDP-galactose pyrophosphatase activities were measured in the endometrium of rat uteri during the oestrous cycle. The galactosyltransferase activity started to increase at dioestrus and reached a maximum on the afternoon of pro-estrus. The UDP-galactose pyrophosphatase activity changed in a direction opposite to that of galactosyltransferase. The sialyltransferase activity was low during metoestrus and dioestrus, but began to rise on the morning of pro-oestrus, reaching a peak on the morning of oestrus. Previously, we have shown that oestradiol administration stimulated galactosyl- and sialyltransferase and inhibited pyrophosphatase activities several-fold in the endometrium of ovariectomized rats. Progesterone prevented the oestradiol effect on the enzymes. The changes in glycosyltransferase and pyrophosphatase activities during the oestrous cycle possibly bear a direct relationship to the ovarian hormones in the rat during the normal oestrous cycle. This relationship will then be conducive to increased synthesis of glycopolymers during ovulation. Furthermore, the lag of 18 h for a maximal rise of sialyltransferase following that of galactosyltransferase is consistent with the normal sequence of glycosylation that occurs in glycoprotein secretion.

Effect of eatradiol and progesterone on UDPgalactose pyrophosphatase activity in the endometrium of ovariectomized rats

Rat endometrium was found to contain a UDPgalactose pyrophosphatase for the hydrolysis of UDPgalactose into galactose 1-phosphate and UMP. The administration of 17β-estradiol to ovariectomized rats resulted in a significant decrease in the activity of the enzyme in endometrium while have little effect on that in myometrium. The response was linear with the dose of estradiol and as little as 0.07 μg per 100 g body weight produced maximum inhibition of the enzyme. Progesterone on its own had little effect on the enzyme activity but in combination with estradiol, it effectively prevented the inhibitory effect of estradiol. This inhibitory effect of estradiol on the activity of UDPgalactose pyrophosphatase may function in the regulation of glycoprotein biosynthesis in endometrium.

Effect of ovarian hormones on glycosyltransferase activities in the endometrium of ovariectomized rats

Some of the properties of galactosyl- and sialyltransferases present in rat endometrial tissue were investigated. The enzyme activities were found to be partly membrane-bound and partly in soluble form. The galactose enzyme was also present in uterine secretions. The specific activities of both galactosyl- and sialyltransferases were greatly enhanced in endometrium of ovariectomized rats following 17 β-estradiol injections, although the enzyme activities in the liver remained unaffected. Mixing experiments with the homogenates of endometrium from control and estradiol-treated rats failed to suggest the presence of any “activator” or “inhibitor” of the enzymes. Diethylstilbesterol, estrone, and estriol also stimulated galactosyl- and sialyltransferase activities, whereas testosterone stimulated sialyltransferase only. Prolactin administration had no effect on either of the enzymes. The effect of estradiol on both enzymes was shown to be dose-dependent and the specific activities of the enzymes started to increase about 6 hr after hormone administration, reaching a peak around 48 h. Progesterone, on its own, had no effect on the galactosyltransferase in ovariectomized rat endometrium but effectively prevented the stimulatory effect of estradiol. When estradiol-primed rats were treated with progesterone, it was found that very small doses of progesterone resulted in decrease of galactosyltransferase activity. In such animals sialyltransferase activity was stimulated by a low concentration of progesterone which was followed by inhibition at higher concentrations. These effects of ovarian hormones on glycosyltransferase activities in endometrium are compatible with earlier reports on the effects of these hormones on glycoprotein and glycosaminoglycan levels in rabbit uterus after ovariectomy (7). Regulation of glycosyltransferase activities in endometrium induced by estradiol and progesterone may bear some relationship to the “receptive” state of the uterus for blastocyst implantation.

Intrauterine grafting in rats of autologous and homologous adult rat skin

Adult skin autografts placed in the rat's uterus were maintained during periods up to 150 days. Implantations occurred only in the contralateral (control) horns. Presence of the ovaries was necessary to the survival and growth of the autografts.Adult skin homografts within the endometrium of whole rats were rejected in the course of the first 15 days.Adult skin homografts within the endometrium of ovariectomized rats under intense estrogenic treatment survived for as long as 60 days.The possible significance of these phenomena is discussed.