共查询到20条相似文献,搜索用时 31 毫秒
1.
Jingwen Hu Kathleen D. Klinich Carl S. Miller Giseli Nazmi Mark D. Pearlman Lawrence W. Schneider Jonathan D. Rupp 《Journal of biomechanics》2009,42(15):2528-2534
Motor-vehicle crashes are the leading cause of fetal deaths resulting from maternal trauma in the United States, and placental abruption is the most common cause of these deaths. To minimize this injury, new assessment tools, such as crash-test dummies and computational models of pregnant women, are needed to evaluate vehicle restraint systems with respect to reducing the risk of placental abruption. Developing these models requires accurate material properties for tissues in the pregnant abdomen under dynamic loading conditions that can occur in crashes. A method has been developed for determining dynamic material properties of human soft tissues that combines results from uniaxial tensile tests, specimen-specific finite-element models based on laser scans that accurately capture non-uniform tissue-specimen geometry, and optimization techniques. The current study applies this method to characterizing material properties of placental tissue. For 21 placenta specimens tested at a strain rate of 12/s, the mean failure strain is 0.472±0.097 and the mean failure stress is 34.80±12.62 kPa. A first-order Ogden material model with ground-state shear modulus (μ) of 23.97±5.52 kPa and exponent (α1) of 3.66±1.90 best fits the test results. The new method provides a nearly 40% error reduction (p<0.001) compared to traditional curve-fitting methods by considering detailed specimen geometry, loading conditions, and dynamic effects from high-speed loading. The proposed method can be applied to determine mechanical properties of other soft biological tissues. 相似文献
2.
Given that automobile crashes are the largest single cause of death for pregnant females, scientists are developing advanced computer models of pregnant occupants. The purpose of this study is to quantify the dynamic material properties of the human uterus in order to increase the biofidelity of these models. A total of 19 dynamic tension tests were performed on pregnant human uterus tissues taken from six separate donors. The tissues were collected during full term Cesarean style deliveries and tested within 36 h of surgery. The tissues were processed into uniform coupon sections and tested at 1.5 strains/s using linear motors. Local stress and strain were determined from load data and optical markers using high speed video. The experiments resulted in a non-linear stress versus strain curves with an overall average peak failure true strain of 0.32±0.112 and a corresponding peak failure true stress of 656.3±483.9 kPa. These are the first data available for the dynamic response of pregnant human uterus tissues, and it is anticipated they will increase the accuracy of future pregnant female computational models. 相似文献
3.
Jérémie Pérès Lionel Thollon Jérome Delotte Yannick Tillier Christian Brunet Kambiz Kayvantash 《Computer methods in biomechanics and biomedical engineering》2014,17(9):958-964
Trauma during pregnancy especially occurring during car crashes leads to many foetal losses. Numerical modelling is widely used in car occupant safety issue and injury mechanisms analysis and is particularly adapted to the pregnant woman. Material modelling of the gravid uterus tissues is crucial for injury risk evaluation especially for the abruption placentae which is widely assumed as the leading cause of foetal loss. Experimental studies on placenta behaviour in tension are reported in the literature, but none in compression to the authors' knowledge. This lack of data is addressed in this study. To complement the already available experimental literature data on the placenta mechanical behaviour and characterise it in a compression loading condition, 80 indentation tests on fresh placentae are presented. Hyperelastic like mean experimental stress versus strain and corridors are exposed. The results of the experimental placenta indentations compared with the tensile literature results tend to show a quasi-symmetrical behaviour of the tissue. An inverse analysis using simple finite element models has permitted to propose parameters for an Ogden material model for the placenta which exhibits a realistic behaviour in both tension and compression. 相似文献
4.
Jérôme Delotte Michel Behr Lionel Thollon André Bongain Christian Brunet 《Computer methods in biomechanics and biomedical engineering》2013,16(4):399-405
The goal of this paper is to study the influence of placenta position on the risk of placenta abruption following a car crash involving a full term pregnant woman in the driver's seat. We developed an anatomically precise finite element numerical model of a pregnant woman. This numerical model was validated using experimental data from crash tests using cadavers given to science. For a frontal impact at a speed of 20 km/h, the mean value of peak strain levels at the utero-placenta interface were found to be close to 20%, independent of placenta position, representing an adverse foetal outcome risk of approximately 15%. This study found no significant effect of placenta position on the risk of placenta abruption. Our anatomically precise approach does however confirm the interest of using a numerical model when studying injury mechanisms in pregnant women involved in car crashes. 相似文献
5.
S A Thompson P F Terranova 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1975,150(2):461-465
Immunoreactive prolactin was measured by RIA in 13.5-15.5 day gestation fetal and 0.5-3.5 day neonatal hamster serum and found to significantly reflect rises and falls in maternal levels. On the average, fetal and neonatal levels were 37% of maternal prolactin serum levels. 125I-PRL injected into 13.5-15.5 day pregnant hamsters was demonstrated to cross the placenta and enter fetal circulation. Ten min after injection, fetal serum levels were calculated to be an average of 3.9% of the radioactivity recorded in maternal serum. There is a strong possibility that fetal prolactin serum levels may be, at least in part, attributed to a maternal source. 相似文献
6.
M K Kalenga R De Hertogh S Whitebread L Vankrieken K Thomas M De Gasparo 《Journal de physiologie》1991,85(4):199-213
1.) Total renin, active renin, prorenin, angiotensin II, estradiol and progesterone were measured in maternal, placental and fetal blood and in trophoblastic and uterine tissues of the guinea pig. Furthermore, membrane angiotensin II receptors were measured in trophoblastic tissues. 2.) Blood and tissue concentrations of total renin, active renin, angiotensin II and steroids are shown to increase with gestational age. At the full term of pregnancy (70th post-coital day), tissue concentrations of total renin in chorion (23,900 +/- 2,752 ng/g of tissue/h), maternal placenta (14,210 +/- 1,131), fetal placenta (12,475 +/- 927) and uterus (7,677 +/- 798) are 100 time higher than those observed in placental, fetal and maternal blood. Distribution of blood and tissue prorenin (inactive renin) is similar to that found for total renin. Active renin/Total renin ratio reaches 1% in uterine, placental and chorion tissues and 9.3 +/- 1.0% in maternal, placental and fetal blood. 3.) Angiotensin II levels in systemic maternal blood (690 +/- 99 pg/ml) and in uterine blood (467 +/- 84) are higher than those found in placental blood (266 +/- 39) and in different trophoblastic tissues (between 200 and 400 pg/g). Angiotensin II receptor concentrations are highest in chorion. 4.) Regarding the steroid hormones, it is noted that placental and maternal blood contain more progesterone than trophoblastic tissues. The highest concentrations of estradiol are found in chorion tissue and uterine blood. 5.) A positive correlation is observed between angiotensin II and estradiol in uterine blood (r = 0.69, P less than 0.01) and in chorion (r = 0.71, P less than 0.01). These findings indicate that angiotensin II and estradiol could, by their interactions, play an important role in the physiology of pregnancy. 相似文献
7.
目的:探讨妊娠合并甲状腺功能亢进症的孕妇的妊娠结局,对母体造成的影响,抗甲状腺药物的使用情况及分娩方式。方法:对23例甲状腺功能亢进孕妇进行了回顾性分析,观察该病对孕妇的影响,对母儿造成的不良结局。结果:23例甲状腺功能亢进孕妇合并轻度妊娠高血压综合征的2例,中度4例,重度2例。合并心衰6例,合并胎膜早破5例,胎盘粘连2例,甲状腺危象1例,胎盘早剥1例,产后出血1例,前置胎盘1例。23例甲状腺功能亢进顺产6例,产钳1例,胎头吸引1例,剖宫产15例。出现早产9例,其中5例为医源性早产。胎儿宫内窘迫6例,死胎1例。结论:妊娠合并甲状腺功能亢进症常危及母婴健康,为降低母儿风险,孕前需很好地控制病情,孕期密切监控,合理治疗。 相似文献
8.
Taylor J Jensen Sung K Kim Zhanyang Zhu Christine Chin Claudia Gebhard Tim Lu Cosmin Deciu Dirk van den Boom Mathias Ehrich 《Genome biology》2015,16(1)
BackgroundCirculating cell-free fetal DNA has enabled non-invasive prenatal fetal aneuploidy testing without direct discrimination of the maternal and fetal DNA. Testing may be improved by specifically enriching the sample material for fetal DNA. DNA methylation may allow for such a separation of DNA; however, this depends on knowledge of the methylomes of circulating cell-free DNA and its cellular contributors.ResultsWe perform whole genome bisulfite sequencing on a set of unmatched samples including circulating cell-free DNA from non-pregnant and pregnant female donors and genomic DNA from maternal buffy coat and placenta samples. We find CpG cytosines within longer fragments are more likely to be methylated. Comparison of the methylomes of placenta and non-pregnant circulating cell-free DNA reveal many of the 51,259 identified differentially methylated regions are located in domains exhibiting consistent placenta hypomethylation across millions of consecutive bases. We find these placenta hypomethylated domains are consistently located within regions exhibiting low CpG and gene density. Differentially methylated regions identified when comparing placenta to non-pregnant circulating cell-free DNA are recapitulated in pregnant circulating cell-free DNA, confirming the ability to detect differential methylation in circulating cell-free DNA mixtures.ConclusionsWe generate methylome maps for four sample types at single-base resolution, identify a link between DNA methylation and fragment length in circulating cell-free DNA, identify differentially methylated regions between sample groups, and uncover the presence of megabase-size placenta hypomethylated domains.
Electronic supplementary material
The online version of this article (doi:10.1186/s13059-015-0645-x) contains supplementary material, which is available to authorized users. 相似文献9.
Johansen B Rakkestad K Balboa MA Dennis EA 《Prostaglandins & other lipid mediators》2000,60(4-6):119-125
Lipid mediators play a crucial role in human parturition and phospholipase A(2) (PLA(2)) is a key regulator of the production of these compounds. We have investigated by PCR the expression of different groups of PLA(2) and COX enzymes in human fetal membranes (amnion and chorion), placenta and three chorionic cell lines (JEG-3, Jar, BeWo). Our data show that the cytosolic Group IV PLA(2) and COX-1 are expressed in all of them, whereas the secretory forms of PLA(2), (Groups IIA, and V), have a more restricted expression. Group IIA mRNA is most abundant in placenta and chorion, whereas Group V PLA(2) mRNA is most abundant in placenta and amnion. On the other hand, COX-2 is present in placenta, chorion and amnion, but was not detected in any of the chorionic cell lines. These results suggest that both cytosolic and distinct secreted forms of PLA(2) could be involved in arachidonic acid (AA) release preceding prostaglandin production at the fetal/maternal interface. 相似文献
10.
《Journal of morphology》2017,278(5):665-674
As part of a broad survey of placental structure, function, and evolution in reptilian sauropsids paraffin‐section histology was used to study microscopic anatomy of the uterus and fetal membranes of three species of North American watersnakes (Nerodia : Colubridae). The pre‐ovulatory uterus is poorly vascularized with inactive shell glands. These shell glands are activated during vitellogenesis but regress during pregnancy. Two placentas develop through apposition of the uterine lining to the chorioallantois and the yolk sac omphalopleure. Fetal and maternal components of the chorioallantoic placenta are progressively vascularized during development. Their epithelia are attenuated, but (contrary to a previous report), epithelia of neither the uterus nor the chorion are eroded. The fetal portion of the yolk sac placenta is an omphalallantois, formed of avascular omphalopleure, isolated yolk mass, and allantois. This placenta is progressively replaced by chorioallantoic placenta during mid‐ to late‐development through depletion of the isolated yolk mass. The chorioallantoic placenta is anatomically specialized for maternal–fetal gas exchange, and its expansion during development reflects the growing needs of the fetus for gas exchange. The yolk sac placenta is morphologically unsuited for gas exchange, but may serve other functions in maternal‐fetal exchange. 相似文献
11.
This work is conducted to investigate the hierarchical structure,mechanical behavior and fracture resistance of grass carp scales with different water contents (hydrated and dehydrated) and load conditions (uniaxial,biaxial and punch tests).The whole cross-section of scales is investigated,and it is found that the bony layer displays discontinuity and partly embeds in collagen layer.Four different locations are considered under both tensile and punch tests.The results of the uniaxial tensile test show a correlation between the failure mode and the distribution of surface morphology on scales.The biaxial test results show that there are minor differences in the tensile strength and the Young'modulus compared with those of the uniaxial tests,but the ultimate strain is about 20%-50%.Puncture tests are also conducted with different size of needles and different hardness silicon rubbers as substrate.The results show that the puncture force and deformation are dependent on the size of needle and the hardness of substrate.The failure pattern of scales is related to the water content.Radial cracks occur in the bony layer of hydrated scale,and the collagen fibers twist around the puncture site.However,the shear failure occurs in the bony layer of dehydrated scale. 相似文献
12.
Incisional hernia development is a significant complication after laparoscopic abdominal surgery. Intra-abdominal pressure (IAP) is known to initiate the extrusion of intestines through the abdominal wall, but there is limited data on the mechanics of IAP generation and the structural properties of rectus sheath. This paper presents an explanation of the mechanics of IAP development, a study of the uniaxial and biaxial tensile properties of porcine rectus sheath, and a simple computational investigation of the tissue. Analysis using Laplace?s law showed a circumferential stress in the abdominal wall of approx. 1.1 MPa due to an IAP of 11 kPa, commonly seen during coughing. Uniaxial and biaxial tensile tests were conducted on samples of porcine rectus sheath to characterise the stress–stretch responses of the tissue. Under uniaxial tension, fibre direction samples failed on average at a stress of 4.5 MPa at a stretch of 1.07 while cross-fibre samples failed at a stress of 1.6 MPa under a stretch of 1.29. Under equi-biaxial tension, failure occurred at 1.6 MPa with the fibre direction stretching to only 1.02 while the cross-fibre direction stretched to 1.13. Uniaxial and biaxial stress–stretch plots are presented allowing detailed modelling of the tissue either in silico or in a surrogate material. An FeBio computational model of the tissue is presented using a combination of an Ogden and an exponential power law model to represent the matrix and fibres respectively. The structural properties of porcine rectus sheath have been characterised and add to the small set of human data in the literature with which it may be possible to develop methods to reduce the incidence of incisional hernia development. 相似文献
13.
Huleihel M Alaa A Olga S E M Levy S Katz M Myatt L Gershon H 《European cytokine network》2003,14(4):229-233
IL-10 is anti-inflammatory cytokine that is involved in the regulation of the pregnancy process. We examined the capacity of fetal and maternal placental tissues from human term placentas, to produce IL-10, in the presence and absence of LPS. The levels of IL-10 were examined (by ELISA and immunohistochemical staining) in the fetal and maternal tissues of human placentas after 10 hours of perfusion, in the presence or absence of lipopolysaccharide (LPS; 1 microg/k"g perfused tissue). We could detect IL-10 in amnion (A; 13.91+/-11.35 pg/ml) and chorion (CH; 7.85 +/- 6.38 pg/ml) tissue homogenates, and in the homogenates of three different sites of the placental tissue compartment (subchorionic placenta (SubCH); 7.39 +/- 4.39 pg/ml, mid-placenta (MidPL); 8.9 +/- 4.73 pg/ml and decidua (Decid); 16.48 + 11.86 pg/ml). Immunohistochemical studies showed that IL-10 was localized in the epithelial cells of the amnion, and in the fibroblasts and macrophages of the chorion. In the placenta and mid-placental sites, IL-10 is localized mainly in cytotrophoblasts and syncytotrophoblasts. The presence of LPS in the perfusion media of the placentas for 10 hours, did not significantly affect the capacity of the fetal and maternal tissues to produce IL-10. Thus, our results may indicate the involvement of the fetal compartment in the down-regulation of the cell-mediated response of the maternal compartment against the fetus, by producing IL-10 under physiological conditions. Infection/inflammation agents such as LPS did not affect the expression levels of IL-10 in the placenta. 相似文献
14.
Riley SC Leask R Selkirk JV Kelly RW Brooks AN Howe DC 《Journal of reproduction and fertility》2000,119(2):329-338
Type 1 NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) is the key enzyme for metabolism of active primary prostaglandins to inactive forms in gestational tissues. The present study examined the activity and immunolocalization of PGDH in the ovine placenta, fetal membranes and uterus over the latter half of pregnancy, and its potential regulation by oestradiol. Placenta, fetal membranes and myometrium were collected from sheep with known single insemination dates on days 70, 100 and 135 of gestation and in active labour demonstrated by electromyographic activity. In addition, chronically catheterized fetuses were infused with oestradiol (100 microgram kg(-1) per 24 h) (n = 5) or saline vehicle into the fetus from day 120 to day 125. PGDH activity measured in placental extracts remained constant from day 70 to day 135 of gestation, and then significantly (P < 0.05) increased by 300% in active labour. Immunoreactive PGDH was localized in the placentome at all stages and was present predominantly in the fetal component of the placentome in uninucleate, but not in binucleate, trophoblast cells. Similarly, in the fetal membranes PGDH immuno-reactivity was present in the uninucleate trophoblast but not in the binucleate cells of the chorion. PGDH immunostaining was also present in the endometrial luminal epithelium, in the smooth muscle of the myometrium, and the glandular epithelium of the cervix. Infusion of oestradiol into the fetal circulation from day 120 to day 125 of gestation had no effect on placental PGDH activity. Immunohistochemistry was used to localize oestrogen receptor alpha in intrauterine tissues to investigate further the failure of oestradiol to increase PGDH activity. Immunoreactive oestrogen receptor alpha was not present in the fetal component of the placenta, although it was expressed in adjacent maternal-derived cells. It is concluded that (1) PGDH activity increases in late gestation; (2) PGDH is expressed in uninucleate trophoblast cells in the ovine placenta and fetal membranes, and also in the maternal endometrial epithelium and stroma, myometrium and cervix; (3) oestrogen receptor alpha is not expressed in fetal cells in the placenta or fetal membranes; and (4) the increase in PGDH activity is not regulated by oestradiol administered to the fetus. 相似文献
15.
Gayle DA Beloosesky R Desai M Amidi F Nuñez SE Ross MG 《American journal of physiology. Regulatory, integrative and comparative physiology》2004,286(6):R1024-R1029
Perinatal infections are a risk factor for fetal neurological pathologies, including cerebral palsy and schizophrenia. Cytokines that are produced as part of the inflammatory response are proposed to partially mediate the neurological injury. This study investigated the effects of intraperitoneal injections of lipopolysaccharide (LPS) to pregnant rats on the production of cytokines and stress markers in the fetal environment. Gestation day 18 pregnant rats were treated with LPS (100 microg/kg body wt i.p.), and maternal serum, amniotic fluid, placenta, chorioamnion, and fetal brain were harvested at 1, 6, 12, and 24 h posttreatment to assay for LPS-induced changes in cytokine protein (ELISA) and mRNA (real-time RT-PCR) levels. We observed induction of proinflammatory cytokines interleukin (IL)-1 beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha) as well as the anti-inflammatory cytokine IL-10 in the maternal serum within 6 h of LPS exposure. Similarly, proinflammatory cytokines were induced in the amniotic fluid in response to LPS; however, no significant induction of IL-10 was observed in the amniotic fluid. LPS-induced mRNA changes included upregulation of the stress-related peptide corticotropin-releasing factor in the fetal whole brain, TNF-alpha, IL-6, and IL-10 in the chorioamnion, and TNF-alpha, IL-1 beta, and IL-6 in the placenta. These findings suggest that maternal infections may lead to an unbalanced inflammatory reaction in the fetal environment that activates the fetal stress axis. 相似文献
16.
Simmons DG Natale DR Begay V Hughes M Leutz A Cross JC 《Development (Cambridge, England)》2008,135(12):2083-2091
The labyrinth of the rodent placenta contains villi that are the site of nutrient exchange between mother and fetus. They are covered by three trophoblast cell types that separate the maternal blood sinusoids from fetal capillaries--a single mononuclear cell that is a subtype of trophoblast giant cell (sinusoidal or S-TGC) with endocrine function and two multinucleated syncytiotrophoblast layers, each resulting from cell-cell fusion, that function in nutrient transport. The developmental origins of these cell types have not previously been elucidated. We report here the discovery of cell-layer-restricted genes in the mid-gestation labyrinth (E12.5-14.5) including Ctsq in S-TGCs (also Hand1-positive), Syna in syncytiotrophoblast layer I (SynT-I), and Gcm1, Cebpa and Synb in syncytiotrophoblast layer II (SynT-II). These genes were also expressed in distinct layers in the chorion as early as E8.5, prior to villous formation. Specifically, Hand1 was expressed in apical cells lining maternal blood spaces (Ctsq is not expressed until E12.5), Syna in a layer immediately below, and Gcm1, Cebpa and Synb in basal cells in contact with the allantois. Cebpa and Synb were co-expressed with Gcm1 and were reduced in Gcm1 mutants. By contrast, Hand1 and Syna expression was unaltered in Gcm1 mutants, suggesting that Gcm1-positive cells are not required for the induction of the other chorion layers. These data indicate that the three differentiated trophoblast cell types in the labyrinth arise from distinct and autonomous precursors in the chorion that are patterned before morphogenesis begins. 相似文献
17.
Radioisotopic tracers were used to measure the unidirectional transfer rates of free fatty acids across the placenta of fed and fasted pregnant guinea pigs. Free (14)C-labeled palmitic and linoleic acids (in serum) were injected simultaneously into a jugular vein of an anesthetized pregnant guinea pig. Serial samples of maternal blood were collected from a carotid artery; fetal blood was collected from the umbilical vein of an exposed fetus. Analysis of maternal and fetal plasma revealed that: (a) the half-lives of free palmitic and linoleic acid in maternal plasma are approximately 1.3 min and 0.7 min, both in fed animals with low plasma concentrations of these acids and in fasted animals with high concentrations; (b) free linoleic and palmitic acids cross the placenta from maternal to fetal plasma in a ratio of approximately 2.0, a value which appears not to change as the transfer rates of these acids from maternal to fetal plasma are increased by fasting the mother. It is suggested that the ratio in which free linoleic and palmitic acids cross the placenta from maternal to fetal plasma is determined by the ratio of the unbound free linoleic and palmitic acid concentrations in maternal plasma. A comparison of several species indicates that a much greater proportion of fetal fatty acids comes from the mother in the guinea pig and rabbit than in the rat, the sheep, or man. 相似文献
18.
The supply of nutrients to the developing fetus is a major function of the human hemochorial placenta, a placenta type in which the fetal chorion is in direct contact with the maternal blood. At term, nutrients have to be transported across two cell layers in chorionic villi, the syncytiotrophoblast (STB) and fetal endothelial cells. The STB is a continuous syncytium covering the entire surface of chorionic villi. This polarized epithelium is specialized in exchange processes and membrane trafficking between the apical membrane facing the maternal blood and the basal membrane facing the fetal endothelium. To meet placental and fetal requirements, the STB selectively takes up and transports a variety of nutrients, hormones, growth factors and cytokines and also transfers passive immunity to the fetus by receptor-mediated transcytosis. In this review in vivo and in vitro systems currently used to study STB functions are discussed and the potential mechanisms of transplacental IgG, iron, lipoprotein and glucose transport are presented. As revealed in this article, the placenta is a tissue where intensive cell biological research is required to unravel endocytic trafficking pathways in a highly specialized cell such as the STB. 相似文献
19.
Finite element aortic injury reconstruction of near side lateral impacts using real world crash data
Belwadi A Siegel JH Singh A Smith JA Yang KH King AI 《Journal of biomechanical engineering》2012,134(1):011006
Traumatic rupture of the aorta (TRA) remains the second most common cause of death associated with motor vehicle crashes, only less prevalent than brain injury. On average, nearly 8000 people die annually in the United States due to blunt injury to the aorta. It is observed that over 80% of occupants who suffer an aortic injury die at the scene due to exsanguination into the chest cavity. In the current study, eight near side lateral impacts, in which TRA occurred, were reconstructed using a combination of real world crash data reported in the Crash Injury Research and Engineering Network (CIREN) database, finite element (FE) models of vehicles, and the Wayne State Human Body Model - II (WSHBM). For the eight CIREN cases reconstructed, the high strain regions in the aorta closely matched with the autopsy data provided. The peak average maximum principal strains in all of the eight CIREN cases were localized in the isthmus region of the aorta, distal to the left subclavian artery, and averaged at 22?±?6.2% while the average maximum pressure in the aorta was found to be 117?±?14.7 kPa. 相似文献
20.
M K Kalenga M de Gasparo S Whitebread L Vankrieken K Thomas R De Hertogh 《Reproduction, nutrition, development》1992,32(1):47-54
Membrane angiotensin II receptors were measured in trophoblastic tissues using a 2-step procedure. The first step consisted of the relative measurement performed at a fixed 125I[Sar1 Ile8]AII concentration of 0.15 nM in order to determine which tissues had a sufficient number of binding sites for studying the competition curves. The second consisted of determining the maximal binding (Bmax) and the dissociation constant (Kd) for [Sar1 Ile8] AII and the receptor subtypes in these tissues. The relative binding measurement revealed a significant number of occupied sites in rabbit fetal placenta and chorion (159 +/- 17 and 51 +/- 10 fmol/mg proteins) and in guinea pig chorion (132 +/- 12). The mean values of the other trophoblastic tissues were 3-10-fold lower in the 2 species. The competition curves obtained from tissues with high angiotensin II binding receptors showed the predominance of the AT2 subtype in rabbit fetal placenta (AT1/AT2 = 25/75) and of the AT1 receptor in guinea pig chorion (97/3) and in rabbit chorion (90/10). The [SAR1 Ile8] AII affinity (Kd) obtained from Scatchard plot analysis was 1.2 +/- 0.2 nM (n = 5) in fetal placenta and 1.2 (n = 1) in rabbit chorion and 0.5 +/- 0.1 (n = 3) in guinea pig chorion. In these tissues, the respective Bmax values were 1,281 +/- 115 (n = 5), 263 (n = 1) and 1,188 +/- 134 fmol/mg proteins (n = 3). These findings indicate that rabbit fetal placenta and chorion and guinea pig chorion are the most important sites of action for the renin-angiotensin system present in trophoblastic tissues. 相似文献