Malignant deciduoid mesothelioma: a rare variant of epithelioid mesothelioma.

We describe a case of a deciduoid mesothelioma, a rare variant of epithelioid mesothelioma, which is associated with a very poor prognosis. A review of the relevant literature is also included. The patient was a man with probable asbestos exposure and presented with classic features of pleural malignancy. Diagnosis was reached with close correlation between clinical, radiological and pathological findings.

Deciduoid mesothelioma of the thorax: A comprehensive review of the scientific literature.

OBJECTIVE: Deciduoid mesothelioma is a rare variant of malignant epithelioid mesothelioma. It often involves the peritoneum, but also thoracic cases have been reported. The aim of the present review is to describe the demographic, clinical, radiological, and pathological features of such a rare variant of thoracic mesothelioma, and the state of the art regarding the therapeutic approaches currently available. DATA SOURCE: English-language articles published from 1985 to June 2016, and related to thoracic deciduoid mesothelioma cases were retrieved using the Pubmed database. STUDY SELECTION: The search terms were "mesothelioma," "thoracic mesothelioma," "epithelial mesothelioma," "pleural mesothelioma," and "deciduoid mesothelioma." RESULTS: Forty-four cases included in 16 articles, published in the period under investigation, were analyzed in detail. CONCLUSIONS: The mean age of the patients was 63 years, and the male to female ratio 1.7:1. Approximately 58% had exposure to asbestos, and 73% had a smoking history; familiarity was rarely reported. The most common anatomical site of origin was the right pleura, and the most frequent clinical manifestations were chest pain, dyspnea, cough, and weight loss. Thoracic X-ray and computed tomography were the imaging techniques most employed for diagnosis and surgical planning. The pathological diagnosis was obtained by examination of surgical or biopsy specimens in most cases. The best treatment strategy of deciduoid mesothelioma is a matter of debate; nevertheless a multidisciplinary approach is currently the best option for the choice of the adequate therapeutic scheme.

Stomatin-like protein 2 is involved in endometrial stromal cell proliferation and differentiation during decidualization in mice and humans.

The molecular mechanisms underlying endometrial stromal cell proliferation and differentiation (decidualization) are still not fully understood. This study revealed that increased Slp-2 expression is a significant factor modulating endometrial stromal cell proliferation and decidualization in both mice and humans. Our results showed a significant difference in the mRNA and protein levels between the implantation site and inter-implantation site on day 5 and day 6 of pregnancy in mice (all P < 0.05). Strong Slp-2 immunostaining was mainly localized within the decidual zone of mice through the post-implantation period. Mice with artificially induced deciduoma showed significantly higher expression of Slp-2 compared with uninduced controls (P < 0.005). Human stromal cells in the middle and late-secretory phases demonstrated significantly (all P < 0.05) upregulated SLP-2, compared with cells in the proliferative phase and early secretory phases. Further analyses of the SLP-2 gene knocked down revealed a significant (P < 0.005) repression of both the decidualization marker gene's expression (decidual/trophoblast prolactin-related protein in mice, insulin-like growth factor binding protein and prolactin in human) and the cell proliferation in in vitro-induced decidualized primary endometrial stromal cells in mice and humans.

Spontaneous decidualization in pseudopregnant rats with vitamin E deficiency.

Successful implantation of an embryo requires adequate depth of invasion in the endometrium, which depends upon decidualization. The aim of the present study was to elucidate why humans experience spontaneous decidualization and menstruation while most other mammals do not. We established a spontaneous decidualization model in pseudopregnant rats with vitamin E deficiency (VED) to investigate mechanisms associated with spontaneous decidualization. Vaginal smears were used to monitor bleeding while vitamin E levels were analyzed with a commercial vitamin E assay kit. Trypan blue staining was used to observe the implantation site at 5.5 days post-coitum (dpc). Uterine morphology, estradiol (E2) and progesterone levels, and the anti-oxidation system were evaluated at 5.5, 7.5, and 9.5 dpc. The proportion of rats in the VED group exhibiting endometrial bleeding gradually increased (5.9%, 32.3%, and 50%) over three consecutive cycles of pseudopregnancy. Vitamin E levels in the VED group were markedly lower compared to the control group in both the plasma and uterus, while the level of vitamin E in the liver did not differ between the control and VED groups. Spontaneous decidualization in the VED group was validated by histological examination and immunohistochemistry. At 5.5 dpc, the mean serum E2 level in the VED group was more than twice that of the control group. The mean total anti-oxidizing capability, catalase level, and glutathione peroxidase activity were significantly reduced in the decidualized portion of the VED group compared to controls, while the malondialdehyde level was also significantly higher in the decidualized portion of the VED group. We hypothesize that the E2 surge at 5.5 dpc and increasing levels of reactive oxygen species are responsible for spontaneous decidualization in VED rats.

Excess Maternal Fructose Consumption Increases Fetal Loss and Impairs Endometrial Decidualization in Mice.

The most significant increase in metabolic syndrome over the previous decade occurred in women of reproductive age, which is alarming given that metabolic syndrome is associated with reproductive problems including subfertility and early pregnancy loss. Individuals with metabolic syndrome often consume excess fructose, and several studies have concluded that excess fructose intake contributes to metabolic syndrome development. Here, we examined the effects of increased fructose consumption on pregnancy outcomes in mice. Female mice fed a high-fructose diet (HFrD) for 6 weeks developed glucose intolerance and mild fatty liver but did not develop other prominent features of metabolic syndrome such as weight gain, hyperglycemia, and hyperinsulinemia. Upon mating, HFrD-exposed mice had lower pregnancy rates and smaller litters at midgestation than chow-fed controls. To explain this phenomenon, we performed artificial decidualization experiments and found that HFrD consumption impaired decidualization. This appeared to be due to decreased circulating progesterone as exogenous progesterone administration rescued decidualization. Furthermore, HFrD intake was associated with decreased bone morphogenetic protein 2 expression and signaling, both of which were restored by exogenous progesterone. Finally, expression of forkhead box O1 and superoxide dismutase 2 [Mn] proteins were decreased in the uteri of HFrD-fed mice, suggesting that HFrD consumption promotes a prooxidative environment in the endometrium. In summary, these data suggest that excess fructose consumption impairs murine fertility by decreasing steroid hormone synthesis and promoting an adverse uterine environment.

Cervical deciduosis imitating dysplasia.

Ectopic cervical deciduosis is generally an accidental finding during pregnancy, and usually presents without any symptoms or need for therapeutic intervention. However, it can sometimes imitate dysplasia or carcinoma. We report a case of a 34-year-old G2P0, with a history of cervical dysplasia, presenting at 11 weeks of gestation, with vaginal blood loss. During examination, lesions mimicking dysplasia were found on the cervix. Histological examination reported cervical deciduosis. Deciduosis is a benign change during pregnancy and will resolve spontaneously. With the increasing use of cytology and colposcopy, the reported incidence is growing. When it is hard to differentiate between dysplasia and deciduosis, histological confirmation should be considered.

Lefty inhibits in vitro decidualization by regulating P57 and cyclin D1 expressions.

Endometrial decidualization is highly important for successful construction and maintenance of embryo implantation and pregnancy. Lefty gene at different menstrual cycle phases has different expressions, indicating its regulatory significance. To study the mechanism of Lefty in decidualization, human endometrial stromal cells (hESCs) were cultured and induced with medroxyprogesterone acetate (MPA) and 8-bromoadenosine-cAMP (8-Br-cAMP) in vitro as a research model. Our results showed that Lefty1 overexpression inhibited MPA- and 8-Br-cAMP-induced hESC decidualization and significantly reduced the secretion of prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP-1). With the inhibition of Lefty1 expression, hESC decidualization induced by MPA and 8-Br-cAMP became more remarkable, and the secretions of PRL and IGFBP-1 were higher too. Further tests indicated that during the process of decidualization, P57 expression increased, whereas cyclin D1 expression decreased. Although Lefty1 overexpression did not significantly change the expressions of P57 and cyclin D1, inhibition of Lefty1 expression resulted in more evident changes in P57 and cyclin D1 expressions. Meanwhile, cell cycle examination showed that Lefty1 overexpression reduced the cell cycle arrest at G1/S phase in the in vitro hESC decidualization model. Therefore, Lefty1 could regulate the cell cycle via modulating the expressions of P57 and cyclin D1 and then inhibit the decidualization in vitro.

Possible roles of the cAMP-mediators EPAC and RAP1 in decidualization of rat uterus.

The optimal decidualization of endometrial stromal cells (ESCs) following embryo implantation is one of the critical steps to establish pregnancy in rodents and humans. This step is intricately regulated by ovarian hormones. Using in vitro human ESCs model, we previously showed that activation of a cAMP mediator, exchange protein directly activated by cAMP (EPAC), promotes ovarian steroid- or cAMP analog-induced decidualization. However, expressions and functions of EPAC and RAP1 in the uterus during pregnancy have not yet been examined. In this study, we found that the expression of EPAC2 and RAP1 was markedly upregulated in the decidual cells at the implantation sites on days 7 and 9 of pregnancy in rats. Furthermore, both delayed-implantation and artificial decidualization models showed that EPAC2 and RAP1 expression was enhanced in decidual cells. Significant activation of cAMP-responsive element-binding protein (CREB), a central transcriptional factor of cAMP signaling, was observed in decidual cells. These spatiotemporal expressions of protein related EPAC pathway are overlapped by sites with activated cAMP signaling, indicating the association of EPAC signaling with decidualization. Strikingly, further studies in in vitro rat decidualization model showed that the cAMP analog and medroxyprogesterone stimulated the expression of decidual markers, while knockdown of EPAC1/2 and RAP1 attenuated the expressions of these markers. Together, these findings suggest that EPAC and RAP1 are the crucial factors for endometrial decidualization in rat pregnancy.

Histerectomía obstétrica por sepsis en el puerperio / Obstetric hysterectomy due to sepsis in the puerperium

Los sangrados de origen obstétrico y las infecciones pélvicas severas constituyen las primeras causas para la realización de una histerectomía en el estado grávido puerperal. La decisión de realizar una histerectomía con un diagnóstico oportuno va a influir en la evolución y pronóstico de estas pacientes. El objetivo principal del presente estudio es analizar la histerectomía obstétrica por procesos infecciosos pélvicos severos, mediante un análisis retrospectivo de 5 años en pacientes del Hospital General de México y del Centro de Esterilidad y Ginecología Integral. Se incluyeron 17 casos de histerectomía obstétrica, el grupo de edad promedio fue entre los 20 y 30 años, la principal indicación fue la deciduomiometritis en el 35,2%, el tiempo promedio de la cirugía fue de 124,4min, las complicaciones principales fueron lesiones al tracto urinario y aquellas secundarias al proceso séptico (CID), la mortalidad fue del 35% (AU)

Bleeding of obstetric origin and severe pelvic infections are the main causes of hysterectomy in the puerperium. Timely diagnosis and hysterectomy influence the outcome of these patients. The main objective of the present study was to analyze obstetric hysterectomy for severe pelvic infectious processes. We retrospectively analyzed obstetric hysterectomies for severe pelvic infectious processes and sepsis in the puerperium performed over a 5-year period in the General Hospital of Mexico. Seventeen cases of obstetric hysterectomy were analyzed. Most patients were aged between 20 and 30 years. The main indication was endometritis in 35.2%, and the mean operating time was 124.4min. The main complications were urinary tract lesions and those secondary to the septic process (disseminated intravascular coagulation). Mortality was 35% (AU)

Expression and function of fatty acid-binding protein 4 during mouse decidualization.

Fatty acid-binding protein 4 (Fabp4) is highly expressed in the secondary decidual zone of mouse decidua and deciduoma and stromal cells under in vitro decidualization. Dtprp, a well-known marker of in vitro decidualization, is diminished by small interfering RNA against Fabp4 and FABP4 inhibitor and stimulated through Fabp4 overexpression.

Antifertility and fetotoxic activities of Acanthus montanus aqueous extract in Wistar rats.

Acanthus montanus T. Anderson (Acanthaceae) possesses several medicinal properties; it is used in Cameroon as a folk medicine to treat pain, inflammation and threatened abortion. The aim of this study was to determine the effect of A. montanus aqueous extract on the estrous cycle pre- and postimplantation in rats and its mechanism of action. The estrous cycles of Wistar rats were monitored before, during and after oral administration of distilled water (control) or aqueous extract (62.5, 125, 250, 500, 1000 mg/kg/day). Furthermore, pregnant rats received the above doses of aqueous extract on days 1-6 (preimplantation) or 6-15 (postimplantation) of gestation and were sacrificed on day 8 or 20 of pregnancy, respectively. Moreover, aqueous extract (500 and 1000 mg/kg/day) was given to ovariectomized rats in the presence or absence of exogenously administered estrogen and/or progesterone and uterine weight and deciduoma count were evaluated. The extract, irrespective of dose, reversibly prolonged the metestrous and occasionally the diestrous stages of the estrous cycle. The extract did not alter the uterine wet weight or deciduoma count, suggesting a lack of estrogenic and progestational effects. At 1000 mg/kg/day, the extract caused appreciable preimplantation losses of 36.8 +/- 6.5% (P < 0.05), while none of the doses caused postimplantation losses. The extract also caused delayed fetal growth.

The conceptus increases secreted phosphoprotein 1 gene expression in the mouse uterus during the progression of decidualization mainly due to its effects on uterine natural killer cells.

Within the mouse endometrium, secreted phosphoprotein 1 (SPP1) gene expression is mainly expressed in the luminal epithelium and some macrophages around the onset of implantation. However, during the progression of decidualization, it is expressed mainly in the mesometrial decidua. To date, the precise cell types responsible for the expression in the mesometrial decidua has not been absolutely identified. The goal of the present study was to assess the expression of SPP1 in uteri of pregnant mice (decidua) during the progression of decidualization and compared it with those undergoing artificially induced decidualization (deciduoma). Significantly (P<0.05) greater steady-state levels of SPP1 mRNA were seen in the decidua when compared with deciduoma. Further, in the decidua, the majority of the SPP1 protein was localized within a subpopulation of granulated uterine natural killer (uNK) cells but not co-localized to their granules. However, in addition to being localized to uNK cells, SPP1 protein was also detected in another cell type(s) that were not epidermal growth factor-like containing mucin-like hormone receptor-like sequence 1 protein-positive immune cells that are known to be present in the uterus at this time. Finally, decidual SPP1 expression dramatically decreased in uteri of interleukin-15-deficient mice that lack uNK cells. In conclusion, SPP1 expression is greater in the mouse decidua when compared with the deciduoma after the onset of implantation during the progression of decidualization. Finally, uNK cells were found to be the major source of SPP1 in the pregnant uterus during decidualization. SPP1 might play a key role in uNK killer cell functions in the uterus during decidualization.

Characterization of a population of unique granular lymphocytes in a bitch deciduoma, using a panel of histo- and immunohistochemical markers.

The ovaries and uterus were collected after ovariohysterectomy from a 16-month-old Labrador bitch in diestrus that never mated. Discrete swellings were found in the uterine horns, with the macroscopic appearance of normal early pregnancy. At histologic examination, the endometrium, devoid of any conceptus and chorion, showed a marked proliferation, on the basis of which a diagnosis of deciduoma was made. A remarkable population of stromal eosinophilic granular lymphocytes was present, especially in the axis of the endometrial folds. Periodic acid-Schiff and Dolichos biflorus-lectin histochemical reaction and a panel of 10 immunohistochemical markers were used to characterize eosinophilic granular cells. Our findings allowed us to compare these granular cells with the granulated decidual cells, whose presence was until now described only in primates, rodents, or a few other epitheliochorial species. On the basis of our results, the importance of eosinophilic granular cells in a decidualization process is hypothesized to occur also in the bitch.

Effect of mifepristone on steroid receptor expression and biotransformation of oestrogen and progesterone in rat uterus and deciduoma.

BACKGROUND: [corrected] Mifepristone is a synthetic antiprogestin which terminates early pregnancy. Since it interferes with the progesterone maintained decidua, we compared the effect of mifepristone on oestrogen and progesterone receptors, and on the biotransformation of these hormones in normal and deciduous uterus. METHODS: Ovariectomized rats were treated with an oestrogen-progesterone hormone regimen and deciduoma was induced by trauma in one horn of the rat uterus while the other served as a control under an identical hormonal milieu. Hormone receptor and biotransformation studies were done using radiolabelled oestradiol and progesterone with high specific activity. RESULTS: The artificially formed decidual tissue was comparable with that of early pregnancy. Mifepristone replenished oestrogen and progesterone receptors which were suppressed by progesterone in both the normal and decidualized uterine horns. Inhibition of oestrogen receptors by progesterone correlated with decreased oestradiol levels at the site of action. Metabolism of progesterone to less potent compounds was promoted by mifepristone. The enzymatic activities of 17beta-hydroxysteroid dehydrogenase (which metabolizes oestradiol), and 20alpha-hydroxysteroid dehydrogenase and 5alpha-reductase (which metabolize progesterone) were altered by mifepristone. CONCLUSION: The effect of mifepristone in varying the hormone receptor population and the availability of different levels of active metabolites of ovarian hormones have an Important role in the antiprogestin action of mifepristone.

Spontaneous deciduosarcoma in a domestic rabbit (Oryctolagus cuniculus).

Deciduosarcoma is a rare, hormonally dependent neoplasm with features of malignancy, previously reported only in rabbits enrolled in chronic toxicology studies involving estrogens with or without progestins. An exploratory laparotomy was performed on a 6-year-old pet Dutch dwarf rabbit following palpation of a 6-cm-diameter abdominal mass. Grossly, the mass was fleshy and nodular, adhered to but not appearing to originate from the small intestine, with a smaller mass of similar appearance involving the uterus, and an effaced mesenteric lymph node. Histologically, the mass was characterized by spindloid cells and large epithelioid cells with abundant pale eosinophilic vacuolated cytoplasm and an infiltrative pattern of growth. Giant cells with large, bizarre, hyperchromatic nuclei were common. Cells were positive by immunohistochemistry for vimentin and progesterone and estrogen receptors and negative for pancytokeratin (AE1/AE3), cytokeratin 18, desmin, alpha-smooth muscle actin (SMA), and CD10. Based on histologic and immunohistochemical findings, a diagnosis of deciduosarcoma was made.

Post-implantation mouse conceptuses produce paracrine signals that regulate the uterine endometrium undergoing decidualization.

The uterus undergoes a series of dramatic changes in response to an implanting conceptus that, in some mammalian species, includes differentiation of the endometrial stroma into decidual tissue. This process, called decidualization, can be induced artificially in rodents indicating that the conceptus may not be essential for a proper maternal response in early pregnancy. In order to test this hypothesis, we determined if and how the conceptus affects uterine gene expression. We identified 5 genes (Angpt1, Angpt2, Dtprp, G1p2 and Prlpa) whose steady-state levels in the uterus undergoing decidualization depends on the presence of a conceptus. In situ hybridization revealed region-specific effects which suggested that various components of the conceptus and more than one signal from the conceptus are likely responsible for altering decidual cell function. Using cell culture models we found that trophoblast giant cells secrete a type I interferon-like molecule which can induce G1p2 expression in endometrial stromal cells. Finally, decidual Prlpa expression was reduced in the uterus adjacent to Hand1- and Ets2-deficient embryos, suggesting that normal trophoblast giant cells in the placenta are required for the conceptus-dependent effects on Prlpa expression in the mesometrial decidua. Overall, these results provide support for the hypothesis that molecular signals from the mouse conceptus have local effects on uterine gene expression during decidualization.

Interstitial trophoblast invasion in the decidua and mesometrial triangle during the last third of pregnancy in the rat.

Like other species with haemochorial placentation, pregnant rats show marked invasion of the uterine wall by trophoblast. While an endovascular pathway of invasion has been recognized for a long time, only recently, by application of cytokeratin immunostaining, the existence of an interstitial pathway of invasion has been established. Interstitial invasion is mainly effected by glycogen cell-like trophoblast arising from glycogen cell islands of the trophospongium opening up into the decidua, and from glycogen cell sheaths surrounding the intraplacental maternal arterial channels which are connected with the spiral arteries in decidua and mesometrial triangle. Quantitative evaluation of interstitial invasion in both maternal compartments was carried out on days 15-21, using PAS staining and cytokeratin and alpha-actin immunostaining for detecting trophoblast and defining maternal tissue compartments. Measurements of compartment size, cytokeratin-positive areas and invasion extent were performed using the KS400 image analysis system. A distinct pattern of interstitial trophoblast invasion emerged, starting from central decidual areas around the maternal arterial channels, and mushrooming into the mesometrial triangle reaching a peak at day 18, followed by gradual regression of the invaded areas. These measurements may serve as a basis for further experiments to evaluate factors which may influence the depth of trophoblast invasion.

Impairment of decidualization in SRC-deficient mice.

Many signaling events induced by ovarian steroid hormones, cytokines, and growth factors are involved in the process of decidualization of human and rodent endometrium. We have reported previously that tyrosine kinase activation of SRC functionally participates in decidualization of human endometrial stromal cells. To address its essential role in decidualization, we examined, using wild-type and Src knockout mice, whether the process of decidualization was impaired in the absence of SRC. Immunohistochemistry using an antibody specific for the active form of SRC revealed that the active SRC was expressed prominently in the decidualizing stromal cells of the pregnant wild-type mouse. Moreover, the active SRC was upregulated in the uterine horn with artificially stimulated decidual reaction. In comparison with wild-type and Src heterozygous mice, the uterus of Src null mice showed no apparent decidual response following artificial stimulation. Ovarian steroid-induced decidualization in vitro, as determined by morphological changes and expression of decidual/trophoblast prolactin-related protein and prostaglandin-endoperoxide synthase 2 (also known as Cox2), both of which are decidualization markers, did not occur in a timely fashion in endometrial stromal cells isolated from the uteri of SRC-deficient mice compared to those from wild-type and Src heterozygous mice. Our results collectively suggest that SRC is an indispensable signaling component for maximal decidualization in mice.

Endovascular trophoblast invasion and associated structural changes in uterine spiral arteries of the pregnant rat.

The involvement of endovascular trophoblast in fibrinoid deposition, replacement of the endothelium and vascular smooth muscle breakdown is studied in spiral arteries of the mesometrial triangle from day 15 to day 21 of rat pregnancy, by examining arterial cross sections after staining for cytokeratin, PAS, CD31 and alpha-actin. From day 15 to day 18 of pregnancy, fibrinoid deposition underneath the endovascular trophoblast increases gradually, whereas the amount of endovascular trophoblast in invaded arteries remains constant. CD31 staining is significantly reduced in sub-ET (= underlying the endovascular trophoblast) as compared to extra-ET (= outside the endovascular trophoblast) and no-ET (= non-invaded arterial sections) at each time-point of pregnancy examined (P < 0.005 and P < 0.0005 at each day of pregnancy), whereas alpha-actin staining is reduced both in sub-ET and in extra-ET as compared to no-ET. During pregnancy, CD31 staining in sub-ET initially declines, but increases significantly on day 21 (P < 0.001 versus d20) suggesting re-endothelialization of the vascular wall. In conclusion, changes in spiral arteries of pregnant rats reveal striking similarities with physiological changes seen in human pregnancy, thus emphasizing the usefulness of this species as an experimental model for studying normal and complicated pregnancies in humans.

Luteal 3beta-hydroxysteroid dehydrogenase and 20alpha-hydroxysteroid dehydrogenase activities in the rat corpus luteum of pseudopregnancy: effect of the deciduoma reaction.

BACKGROUND: In the rat, the maintenance of gestation is dependent on progesterone production from the corpora lutea (CL), which are under the control of pituitary, decidual and placental hormones. The luteal metabolism of progesterone during gestation has been amply studied. However, the regulation of progesterone synthesis and degradation during pseudopregnancy (PSP), in which the CL are mainly under the control of pituitary prolactin (PRL), is not well known. The objectives of this investigation were: i) to study the luteal metabolism of progesterone during PSP by measuring the activities of the enzymes 3beta-hydroxysteroid dehydrogenase (3betaHSD), involved in progesterone biosynthesis, and that of 20alpha-hydroxysteroid dehydrogenase (20alphaHSD), involved in progesterone catabolism; and ii) to determine the role of decidualization on progesterone metabolism in PSP. METHODS: PSP was induced mechanically at 10:00 h on the estrus of 4-day cycling Wistar rats, and the stimulus for decidualization was provided by scratching the uterus on day 4 of PSP. 3betaHSD and 20alphaHSD activities were measured in the CL isolated from ovaries of PSP rats using a spectrophotometric method. Serum concentrations of progesterone, PRL, androstenedione, and estradiol were measured by radioimmunoassay (RIA). RESULTS: The PSP stage induced mechanically in cycling rats lasted 11.3 +/- 0.09 days (n = 14). Serum progesterone concentration was high until day 10 of PSP, and declined thereafter. Serum PRL concentration was high on the first days of PSP but decreased significantly from days 6 to 9, having minimal values on days 10 and 11. Luteal 3betaHSD activities were elevated until day 6 of PSP, after which they progressively declined, reaching minimal values at the end of PSP. Luteal 20alphaHSD activities were very low until day 9, but abruptly increased at the end of PSP. When the deciduoma was induced by scratching the uterus of pseudopregnant animals on day 4 (PSP+D), PSP was extended to 18 +/- 2.2 days (n = 8). In PSP + D rats, serum progesterone and PRL levels, and luteal 3betaHSD activities were higher than in pseudopregnant rats on day 11. Decidualization also prevented the increase in luteal 20alphaHSD activities observed on day 11 of PSP. Administration of the dopaminergic agonist CB154 in PSP + D rats on day 10 of PSP induced a decline in both serum PRL and progesterone on day 11 of PSP, values that were not different from that of pseudopregnant controls. CONCLUSIONS: We have established that during the final period of PSP a decline in progesterone biosynthesis occurs before the increase in progesterone catabolism. We have also shown that decidualization in pseudopregnant rats extends the life of the CL by prolonging the production of pituitary PRL, and by maintaining high 3betaHSD and low 20alphaHSD activities within the CL leading to sustained production of progesterone.