Effect of IUDs, prostaglandins and indomethacin on decidual cell reaction in the rat

Effect of prostaglandin E2 on rate of decidualization in rats

Based on morphology, it has been suggested that prostaglandin E2 (PGE2) accelerates the process of endometrial stromal cell differentiation to decidual cells in the rat. The present study investigated this possibility, using changes in uterine weight and in endometrial alkaline phosphatase (ALP) activity as indicators of decidualization. Rats were ovariectomized and treated with one of two steroid protocols; the first was identical to that previously used for the study of morphology, the second a modified protocol which results in greater uterine sensitization for decidualization, producing larger amounts of decidual tissue, thereby making it easier to detect differences between treatments. On the day of uterine sensitization, rats within each treatment protocol were given a unilateral intrauterine infusion of phosphate-buffered saline (PBS) or PGE2 plus indomethacin, and killed 24, 48 or 72 h later. The time-courses for the increases in uterine weight and ALP activity in uterine horns infused with PBS or PGE2 plus indomethacin differed between steroid protocols, but within a protocol were statistically indistinguishable. The results do not support the hypothesis that PGE2 accelerates the process of decidualization but do provide additional support for the notion that PGE2 is a physiological rather than pharmacological mediator of decidualization.

Effect of indomethacin and prostaglandin E2 on structural differentiation of rat endometrium during artificially induced decidualization

Morphological differentiation of uterine stromal and luminal epithelial cells was studied in steroid-injected ovariectomized rats following unilateral intrauterine instillation of sesame oil, phosphate-buffered saline containing gelatin (PBSG), PBSG + indomethacin (IM; an inhibitor of prostaglandin synthesis), or PBSG + IM + prostaglandin E2 (PGE2). The latter two treatments were preceded by a subcutaneous injection of IM. Uteri were examined by light and electron microscopy at intervals between 8 and 120 hr (n = 4/treatment/time). Differentiation began in the periluminal antimesometrial region and progressed peripherally and towards the mesometrial aspect in all groups. Structural features and timing of differentiation were similar for oil-injected and PBSG-infused uteri. Administration of IM inhibited the onset of the decidual cell reaction and had deleterious effects on the luminal epithelium. Inclusion of PGE2 in the instillate accelerated stromal cell differentiation and overcame the inhibitory effect of IM. The results implicate prostaglandins, particularly PGE2, in endometrial transformation during decidualization.

Effect of phorbol ester on prostaglandin regulation of proliferation in rabbit endometrial cells

We have proposed that two of the endogenously synthesized endometrial prostaglandins, prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E1 (PGE1), play a regulatory role in growth control of the endometrium. PGF2 alpha increases DNA synthesis and PGE1 inhibits that effect. Primary cultures of rabbit endometrial cells were used here to examine the effects of the tumor-promoting, diacylglycerol mimicking, phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate (TPA), on the prostaglandin control of cell proliferation. TPA treatment of these cultures results in: a decrease in control levels of proliferation and complete inhibition by TPA of PGF2 alpha stimulated DNA synthesis; a reduction in [3H]PGF2 alpha binding with short term treatment but an increase to above control binding level with long term treatment; an inhibition of the normal PGF2 alpha stimulated inositol polyphosphate synthesis; and a small increase in accumulation of PGF2 alpha in the culture media. Furthermore, in this culture system, TPA does not down regulate [3H]PGE1 binding; it does not alter the normal PGE1 stimulation of cAMP synthesis; and it has no effect on the normal endogenous PGE1 synthesis by these cultures. The above results are consistent with our previous observations that PGF2 alpha works through the intracellular messengers inositol polyphosphate/diacylglycerol whereas PGE1 works through cAMP.

Requirement for prostaglandin F2 alpha in 17 beta-estradiol stimulation of DNA synthesis in rabbit endometrial cultures

We have hypothesized that two of the endogenously synthesized endometrial prostaglandins (PGs), prostaglandin F2 alpha (PGF2 alpha), and prostaglandin E1 (PGE1), play a regulatory role in growth control of the rabbit endometrium. PGF2 alpha increases DNA synthesis and PGE1 inhibits that effect. Primary cultures of rabbit endometrial cells were used to examine the possible role of these PGs in the mechanism of action of 17 beta-estradiol on DNA synthesis. Towards this end, binding, second messenger and DNA synthesis experiments were performed. 17 beta-estradiol stimulation resulted in a time dependent (optimal: approximately 6 h) and 17 beta-estradiol concentration dependent (optimal: approximately 10(-7) M 17 beta-estradiol in phenol red-containing medium) increase in [3H]PGF2 alpha binding. Scatchard type analysis of the binding data revealed an increase in receptor number while the receptor affinity for [3H]PGF2 alpha remained the same as in the control treated cultures. This 17 beta-estradiol stimulated increase in PGF2 alpha receptor allowed a suboptimal concentration of PGF2 alpha (10(-9) M) to increase intracellular levels of inositol polyphosphates, while by itself this concentration of PGF2 alpha caused no significant change in intracellular inositol polyphosphate levels. 17 beta-estradiol, alone among the several studied steroid hormones, could increase [3H]PGF2 alpha binding. Proliferation studies revealed that, in these primary cultures of rabbit endometrium, 17 beta-estradiol could increase DNA synthesis but not in the presence of indomethacin, unless PGF2 alpha was added to the medium at a concentration (10(-10) M) near or above what is normally accumulated in the medium by these cultures. In the absence of 17 beta-estradiol stimulation, addition of these same low concentrations of PGF2 alpha had no effect on DNA synthesis. Apparently, through its effect on the PGF2 alpha receptor, 17 beta-estradiol enhances the PGF2 alpha stimulated DNA synthesis response approximately 100 fold. The DNA synthesis induced by 17 beta-estradiol can be inhibited by PGE1, as can PGF2 alpha-induced DNA synthesis. We propose that 17 beta-estradiol may be mediating its mitogenic effect through an alteration of the prostaglandin agonist:antagonist control of proliferation in rabbit endometrial cultures. In addition we suggest that, if 17 beta-estradiol acts to increase PGF2 alpha, receptors as part of its mode of action, this may be of importance in other tissues possessing both prostaglandin and 17 beta-estradiol receptors.

Regulation of inositol phosphate levels by prostaglandins in cultured endometrial cells

Stimulation of cultured rabbit endometrial cells by one of the rabbit endometrial cell culture proliferation factors, prostaglandin F2 alpha (PGF2 alpha), resulted in a very rapid increase in the intracellular levels of [3H]-inositol triphosphate (IP3), [3H]-inositol biphosphate (IP2), and [3H]-inositol monophosphate (IP1) in cells prelabeled with [3H]-inositol. These increases in inositol phosphate levels were detected in periods of stimulation as short as 30 seconds, reached a maximum by 1 1/2-2 min and declined to control levels by 6-10 min. The stimulation was dose-dependent with maximal increases observed near 10(-6) M PGF2 alpha. The cholinergic agent, carbachol, also led to time and dose-independent increases in IP3. Lithium, cadmium, silver, copper, and zinc ions had no effect either on the breakdown of IP3 or on the accumulation of IP1. In contrast, vanadate at 10(-6) or 10(-5) M did lead to a decrease in the breakdown of IP1 and a concomitant increase in IP1, IP2, and IP3. PGF2 alpha was found previously to induce an increase in rabbit endometrial cell DNA synthesis which was inhibited by concomitant or prior addition of prostaglandin E1 (PGE1). PGE1, in a dose-dependent manner, was found to inhibit the observed IP3 increase by PGF2 alpha at 1 1/2 min of stimulation. PGF2 alpha treated and control cultures did not differ in cAMP or cGMP levels, cellular 45Ca uptake, nor cellular 22Na uptake. We propose that IP3 may be one of the intracellular messenger(s) synthesized following the treatment of rabbit endometrial cell cultures with the proliferation agent PGF2 alpha and that it may play a crucial role with cAMP in growth regulation.

Prostaglandin F2 alpha and E1 regulation of proliferation in primary cultures of rabbit endometrial cells

The study of growth of endometrial cells is of importance in reproductive biology. Several factors and hormones are thought to play important roles in the control of growth. Prostaglandin F2 alpha (PGF2 alpha) causes an increase in both tritiated thymidine ([3H]Tdr) incorporation into DNA and in the cell number of primary cultures of rabbit endometrial cells cultured in a serum-free, chemically defined media. Prostaglandins F1 alpha, E1, E2, A2, and B2 and arachidonic acid (all tested at 10(-7) M) do not affect [3H]Tdr incorporation as compared to control cultures. The increase in [3H]Tdr incorporation into DNA in response to PGF2 alpha stimulation is concentration-dependent (optimal approximately 3 X 10(-7) M) and is seen starting approximately 9 hr poststimulation. Both prostaglandin E1 (PGE1) and prostaglandin E2 (PGE2), but not PGs F1 alpha, I2, A2, B2, their parent molecules, or related molecules, antagonize and can completely block the PGF2 alpha-induced increase in [3H]Tdr incorporation into DNA. This antagonism is seen both when the cells are pretreated with PGE1 prior to the PGF2 alpha stimulation and when the cells are exposed to both PGE1 and PGF2 alpha simultaneously. Exogenously added 8-Br-cAMP mimics the PGE1 antagonism of PGF2 alpha. The PGF2 alpha-induced increase in [3H]Tdr incorporation is not synergistic, antagonistic, or additive with the [3H]Tdr incorporation increase in response to either estradiol-17 beta or epidermal growth factor. The specific effect of PGF2 alpha on primary culture endometrial cell growth and its antagonism by PGE1, PGE2, and 8-Br-cAMP are new findings.

Human endometrial prostaglandin E2 binding sites and their profiles during the menstrual cycle and in pathologic states

Endometrial tissue from uteri of 35 nonpregnant, premenopausal women was assayed for prostaglandin E2 and F2 alpha binding site content as a function of the phase of the menstrual cycle and the pathologic state. For all specimens, tritium-labeled prostaglandin F2 alpha, binding was very low (less than 8 fmol/mg of protein) or undetectable regardless of the phase of the menstrual cycle or pathologic state or in the presence or absence of 10 mumol/L of indomethacin, a prostaglandin synthetase inhibitor. However, tritium-labeled prostaglandin E2 binding was detected in every specimen and was independent of the presence or absence of indomethacin. Binding of tritium-labeled prostaglandin E2, as determined by Scatchard analyses, was biphasic (dissociation constant approximately 1 nmol/L; dissociation constant for low-affinity sites approximately 10 nmol/L) for both proliferative and secretory endometrial tissue. However, the total number of prostaglandin E2 binding sites, determined from Scatchard or single-point analyses, was significantly higher (p less than 0.01) in proliferative endometrium compared to secretory endometrium. In addition, for endometrium from the proliferative phase of the menstrual cycle, the diagnosis of abnormal uterine bleeding was associated with higher (p less than 0.01) tritium-labeled prostaglandin E2 binding than diagnosis of dysmenorrhea, stress urinary incontinence and uterine prolapse, or pelvic inflammatory disease. Endometrial specimens with the last four diagnoses did not differ significantly (p greater than 0.1) from each other.

Influence of indomethacin delivered from an intrauterine silastic device on basal levels and synthesizing capability of rat uterus for prostacyclin

The intrauterine release of indomethacin (approximately 120 micrograms over 23 days) from a unilateral silastic device did not cause any significant reduction in basal levels of PGI2 (determined as 6-keto PGF1 alpha) in the tissue of the IUD horn. However, this tissue was found to have an increased potential for PGI2 synthesis when compared to that of the uterine horn with a plain device. The implications of these findings regarding a possible effect of indomethacin on the myometrium are discussed.

Inhibition of artificially induced decidual cell reaction by indomethacin in the mature oophorectomized rat

Prostaglandin F2 alpha (PGF2 alpha) is capable of inducing a decidual cell reaction (DCR) in the hormonally prepared rat. In the present work indomethacin, a PG synthetase inhibitor, was used to determine whether PGF2 alpha is involved in the DCR induced by artificial stimulation of the endometrium. Thirty-seven animals were oophorectomized and subsequently given daily injections of progesterone for 6 days and one injection of estradiol 17 beta on the fourth day. Later on the fourth day, one of several experimental maneuvers was carried out on the right uterine horn of each animal; these included: 1) introduction of phosphate-buffered saline (PBS) twice into the uterus, 2) intrauterine injection of PGF2 alpha with no subsequent application or manipulation, 3) intrauterine injection of indomethacin followed by subsequent injection of PGF2 alpha, 4) intrauterine injection of indomethacin with subsequent artificial stimulation (scratch), 5) intrauterine injection of PBS with subsequent scratch, 6) scratch followed by injection of PBS, and 7) scratch followed by a second scratch. The extent of the ensuing DCR was assessed 48 h later by measurement of horn weight, by light and electron microscopy, by ranking the DCR, and by the mitotic index. Indomethacin significantly reduced the horn weight in animals treated with scratch but had a much less marked effect on animals treated with PGF2 alpha. Similarly the rank of the DCR and the mitotic index were significantly less in endometria treated by indomethacin with scratch than those treated by indomethacin with PGF2 alpha. From these findings it was concluded that the DCR induced by scratch was inhibited, but not abolished, when preceded by indomethacin. Conversely the DCR induced by PGF2 alpha was not inhibited by indomethacin, thus demonstrating that when local generation of PG is reduced or abolished, PGF2 alpha can sustain the decidual cell response.

Decidual cell reaction induced by prostaglandin F2 alpha in the mature oöphorectomized rat

Sprague-Dawley rats were oöphorectomized and after a 2-3 week recovery period were given daily injections of progesterone (2.0 mg/0.1 ml) for six consecutive days. On the fourth day of progesterone treatment 0.2 microgram of estradiol 17 beta was given in addition and the right uterine cornua were subjected to one of five experimental maneuvers. On the sixth day of progesterone treatment the uterine cornua were weighed and processed for light and electron microscopy. The weights of all left cornua (84.6 +/- 3.7 mg) and the right cornua of PBS-injected (93.3 +/- 11.5 mg) and sham operated uteri (83.6 +/- 19.8 mg) were comparable. A significant increase (p less than 0.001) in weight was found in cornua that received PGF2 alpha (144 +/- 6.7 mg), PGF2 alpha with mild local trauma (scratch) (146 +/- 28.0 mg), and scratch alone (162 +/- 12.7 mg). The majority to cornua treated by scratch alone, or by PGF2 alpha with or without scratch, showed a decidual cell reaction by light microscopy and had a significantly higher mitotic index than those treated with saline, or by sham operation. When specimens were evaluated for the presence of the DCR, the highest rank was found in tissues treated by scratch alone or by PGF2 alpha with or without scratch. Morphometric evaluation by light microscopy indicated that the extent of decidualization in PGF2 alpha-treated tissue was comparable to that of scratch-treated tissue. Ultrastructural observation of PGF2 alpha-treated tissue revealed that decidual cells closely resembled those treated with scratch. However, electron microscopic morphometry revealed that cells that responded to PGF2 alpha had higher volume and surface densities of organelles associated with metabolic activity than did cells responding to scratch alone. These results demonstrate that locally administered PGF2 alpha can initiate, in the hormonally prepared mature oöphorectomized rat, a DCR comparable to that induced by local trauma.

Prostaglandin F2alpha conceptus-endometrial interaction during early gestation in the mouse

Pregnant Swiss-Webster mice were treated subcutaneously with 50, 100 or 200 microgram PGF2alpha on day 4, 5 or 6 postcoitum (p.c.). Twelve hours later, the animals were killed by intracardiac perfusion with Karnovsky's fixative, uteri were removed and a transverse central slice from each implantation site was embedded in Araldite. The conceptus was found by thick sectioning. Thin sections were taken of each implantation site and examined at the electron microscopic level. PGF2alpha administered at a dose of 100 microgram per animal on day 4 p.c. altered the normal attachment of the blastocyst to the endometrium, as well as formation of the implantation chamber. Cytology of the epiblast and hypoblast was adversely affected by this change. Dosages of 100 or 200 microgram PGF2alpha per animal adversely affected the apical trophectoderm cell of the blastocyst. Treatment with PGF2alpha on day 4 p.c. at a dose of 50 microgram per animal reduced the decidual reaction around the implantation chamber while treatment on day 5 p.c. at a dose of 50 or 100 microgram per animal was associated with an advanced stage of development. Treatment on day 6 p.c. did not appear to have any influence on implantation or blastocyst development.

The degenerative effect on rabbit implantation sites by indomethacin. I. Timing of indomethacin action, possible effect on uterine proteins and the effect of replacement doses of PGF2 alpha

To determine the effective time of indomethacin (Id) action in disrupting early pregnancy, groups of rabbits were treated at various stages after mating with Id and/or replacement doses of PGF2 alpha. Effect of Id on the secretion of uterine proteins was also investigated. The highest rate of embryonic death occurred when Id was injected twice daily during days 5-7 of pregnancy, and days 5-6 appear to be the most critical. Persisting levels of Id during this critical stage is required to induce the antifertility effect. The results also indicate that the adverse effect of Id is not mediated through an effect on uterine proteins, and is mainly due to the inhibition of PG's synthesis. PG's are apparently required for normal implantation and early development.

Uterine prostaglandin levels following stimulation of the decidual cell reaction: effects of indomethacin and tranylcypromine

Prostaglandin E (PGE) and F (PGF) levels were measured in mouse uteri at various times after either trauma (hemostat crusing) or oil stimulation of the decidual cell reaction (DCR). The oil induced DCR led to an early increase (within 5 min) in both PGE and PGF levels. Both returned to baseline by 1 h after stimulation. A second peak in PGF levels was observed at 120 min after oil stimulation. This study demonstrates a distinct difference between the pattern of PGE and PGF changes in the uterus following oil stimulation of the DCR. Indomethacin pretreatment completely blocked the oil stimulated DCR as well as all prostaglandin increases following either stimulus. The trauma stimulated DCR was not completely blocked by indomethacin pretreatment. Pretreatment with tranylcypromine, an inhibitor of prostacyclin biosynthesis, did not block the prostaglandin E and F increases, but did block the oil stimulated DCR. These findings suggest that prostacyclin may be an early mediator of the DCR.

Effects of PGE1 or PGE2 on luteal function in pseudopregnant rats

Effects of PGE1 or PGE2 on luteal function were studied in 163 pseudopregnant rats. PGE1 (10, 100, or 300 micrograms) given intrauterine every 6 hr did not shorten pseudopregnancy (P greater than 0.05), however, the same doses of PGE2 given intrauterine every 6 hr advanced luteolysis (P less than 0.05). PGE1 (100 or 300 micrograms) given every 4 hr intramuscular maintained levels of progesterone in peripheral blood above controls (P less than 0.05) while 100 or 300 micrograms of PGE2 hastened the decline in progesterone (P less than 0.05). The antiluteolytic effect of PGE1 was not via an inhibition of PGF secretion (P greater than 0.05) by the uterus or by induction of ovulation in treated animals. Moreover, PGE1 (100, 200, or 500 micrograms) given intramuscular every 4 hr from day 4 of pseudopregnancy until the next proestrus delayed luteal regression around 3 days (P less than 0.05). PGE2 at doses of 100, 200, or 500 micrograms every 4 hr given intramuscular consistently shortened pseudopregnancy (P less than 0.05). Lower doses were without effect (P greater than 0.05). Based on the above data it is concluded that PGE2 is consistently luteolytic whereas PGE1 is not luteolytic in pseudopregnant rats and that PGE1 may be an antiluteolysin.

The effect of prostaglandins F2alpha and E2 on pregnancy in mice during implantation

The uterine content of prostaglandins (PGs) increases following insertion of an intrauterine device (IUD). Such IUD-bearing uteri also exhibit impaired decidualization. Although prostaglandins have been shown to be luteolytic in several species, it is not clear that inhibition of decidualization is mediated solely through alterations in ovarian steroidogenesis. In these experiments, ovariectomized, hormone-replaced pregnant mice, as well as intact mice, were treated systemically with either PGE2 or PGF2alpha so that the extraovarian actions of prostaglandins upon decidualization could be segregated from effects mediated by alterations in ovarian steroidogenesis. The results suggest that the effect of PGF2alpha upon decidualization was mediated via an alteration in ovarian steroidogenesis, but that PGE2 acted independently of the ovary. The hypothesis is presented that alterations in the ratio of E to F prostaglandins elicited within the endometrium by an IUD inhibit decidualization at the uterine level, and that this effect might be mediated by impairment of histamine release from endometrial mast cells.

Effects of indomethacin on uterine capillary permeability and blastocyst development in rabbits

Increased capillary permeability at implantation sites was demonstrated in rabbits by extravasation of intravascular blue dye on day 7 of pregnancy. Subcutaneous administration of indomethacin (Id, 8 mg/kg twice daily) on days 4-6 of pregnancy inhibited this uterine blueing response and appeared to reduce the size of implantation swellings. To test the latter observation blastocyst diameter and development of the embryonic disk were assessed at 144 hr post coitum. In females receiving indomethacin at the dose level which inhibited uterine blueing, blastocysts were significantly smaller than those from control females. Developmental staging of embryonic disks revealed only slight differences between the smaller (Id-treated) blastocysts and control blastocysts. No effect of Id was seen on ovarian function as judged by luteal weights and plasma progesterone and estradiol levels. Since the major biological effects of indomethacin are due to its inhibition of prostaglandin synthesis, it appears that prostaglandins may play a role in the uterine response to blastocyst stimulation and in the expansion of blastocysts in the rabbit.

Studies on the effects of pharmacologic doses of cortisone acetate and several nonsteroidal anti-inflammatory compounds on ovo-implantation, early pregnancy, and the deciduomal response in the rat

Cortisone acetate (10 mg/day), alone or in combination with progesterone (4 mg/day); progesterone (4 mg/day); progesterone (4 mg/day) plus estrone (1 microng/day); indomethacin (0.75 mg/day); phenylbutazone (20 mg/day); flufenamic acid (10 mg/day); and Compound 83161 (tetrazolo less than 1,5-alpha greater than s-triazolo less than 3,4-c greater than quinoxoline) (8 mg/day and 12 mg/day) were each given to intact rats during early pregnancy (days 1 and/or 2 through day 8). Only cortisone acetate treatment caused a true delay in ovo-implantation. Both progesterone treatment beginning on day 1 and cortisone acetate treatment beginning on day 1 or 2 caused an increased postimplantation fetal death rate. Compound 83161, at doses causing signs of general toxicity (12 mg/day), caused a marginal inhibition of implantation. Treatment with indomethacin, phenylbutazone, or flufenamic acid caused some inhibition of the traumatic deciduomal response in spayed rats treated with progesterone, while treatment with cortisone acetate and Compound 83161 did not.