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Transport of monoamines across the human placental brush border membrane
Abstracts
389
TRANSPORT OF MONOAMINES ACROSS THE HUMAN PLACENTAL BRUSH BORDER MEMBRANE V. Ganapathy & F. H. Leibach (Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA) The transport characteristics of three monoamines, serotonin, dopamine and norepinephrine, were investigated in human placental brush border membrane (PBBM) vesicles. Uptake of all three monoamines in these vesicles was stimulated by a NaCl gradient. Both ionic components of the gradient were obligatory. Kinetic studies revealed that two Na+ and one Cl- were involved per transport of one monoamine molecule. These similarities notwithstanding, competition experiments revealed that two distinct transport systems were responsible for the uptake of these monoamines, one specific for serotonin and the other for dopamine and norepinephrine. The affinity of the former system for serotonin was two orders of magnitude greater than the affinity for dopamine and norepinephrine. In contrast, the reverse was true for the latter system. The two systems were also easily distinguishable with respect to various inhibitors. The characteristics of dopamine uptake and norepinephrine uptake were the same, suggesting the involvement of a single system. The specificity of the inhibitors of this system showed that it was similar to the norepinephrine transporter rather than the dopamine transporter described in the brain. We conclude that, 1) the PBBM possesses two distinct monoamine transporters, namely the serotonin transporter and the norepinephrine transporter, 2) the latter system accepts norepinephrine as well as dopamine as substrates, and 3) the specific dopamine transporter known to be present in the brain is absent in the PBBM. (Supported by NIH Grants HD22 103 and HD2445 1.)
FIRST TRIMESTER CHORIONIC VILLOUS EXPLANTS IN CULTURE AS A MODEL TO STUDY THE ORIGIN AND CHARACTERISTICS OF EXTRAVILLOUS CYTOTROPHOBLAST 0. GenbaEev, N. Pap%, M. Cuperlovi~, Lj. ViCovac, M. VuEkovid & R. K. Miller” (Institute for the Application of Nuclear Energy, Zemun, Yugoslavia and the ‘Department of Obstetrics/Gynaecology, University of Rochester, NY 14642, USA) First trimester villi are the source of extravillous cytotrophoblast (EVC). We have cultured such villous tissue in an enriched collagen gel supplemented with different decidual extract preparations mimicking the in vivo situation as closely as possible. Explants were fully embedded or cultured on the surface of the gel. To monitor maintenance of tissue function, daily measurements of human chorionic gonadotrophin (hCG) and progesterone (P) were made over at least 5 and up to 21 days of culture. The production rate of hCG and P increased or remained constant and was comparable with the corresponding pattern in viva. Histological evaluation of the tissue confirmed that the villi were not impaired in culture and that the appearance of EVC was not due to tissue damage induced in vitro. By culturing villous explants on the surface of the gel, the functional integrity of the tissue was better preserved and the EVC migration started after 24-48 h of culture. Two morphologically different types of cells were seen in the migrating population and have been characterized by immunochemistry using lectin binding and different antibodies (gangliosides, human placental lactogen-hPL, plasminogen activator inhibitor). This model seems to offer a method additional to cell culture for studying the origin, behaviour and markers of EVC.
389
TRANSPORT OF MONOAMINES ACROSS THE HUMAN PLACENTAL BRUSH BORDER MEMBRANE V. Ganapathy & F. H. Leibach (Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA) The transport characteristics of three monoamines, serotonin, dopamine and norepinephrine, were investigated in human placental brush border membrane (PBBM) vesicles. Uptake of all three monoamines in these vesicles was stimulated by a NaCl gradient. Both ionic components of the gradient were obligatory. Kinetic studies revealed that two Na+ and one Cl- were involved per transport of one monoamine molecule. These similarities notwithstanding, competition experiments revealed that two distinct transport systems were responsible for the uptake of these monoamines, one specific for serotonin and the other for dopamine and norepinephrine. The affinity of the former system for serotonin was two orders of magnitude greater than the affinity for dopamine and norepinephrine. In contrast, the reverse was true for the latter system. The two systems were also easily distinguishable with respect to various inhibitors. The characteristics of dopamine uptake and norepinephrine uptake were the same, suggesting the involvement of a single system. The specificity of the inhibitors of this system showed that it was similar to the norepinephrine transporter rather than the dopamine transporter described in the brain. We conclude that, 1) the PBBM possesses two distinct monoamine transporters, namely the serotonin transporter and the norepinephrine transporter, 2) the latter system accepts norepinephrine as well as dopamine as substrates, and 3) the specific dopamine transporter known to be present in the brain is absent in the PBBM. (Supported by NIH Grants HD22 103 and HD2445 1.)
FIRST TRIMESTER CHORIONIC VILLOUS EXPLANTS IN CULTURE AS A MODEL TO STUDY THE ORIGIN AND CHARACTERISTICS OF EXTRAVILLOUS CYTOTROPHOBLAST 0. GenbaEev, N. Pap%, M. Cuperlovi~, Lj. ViCovac, M. VuEkovid & R. K. Miller” (Institute for the Application of Nuclear Energy, Zemun, Yugoslavia and the ‘Department of Obstetrics/Gynaecology, University of Rochester, NY 14642, USA) First trimester villi are the source of extravillous cytotrophoblast (EVC). We have cultured such villous tissue in an enriched collagen gel supplemented with different decidual extract preparations mimicking the in vivo situation as closely as possible. Explants were fully embedded or cultured on the surface of the gel. To monitor maintenance of tissue function, daily measurements of human chorionic gonadotrophin (hCG) and progesterone (P) were made over at least 5 and up to 21 days of culture. The production rate of hCG and P increased or remained constant and was comparable with the corresponding pattern in viva. Histological evaluation of the tissue confirmed that the villi were not impaired in culture and that the appearance of EVC was not due to tissue damage induced in vitro. By culturing villous explants on the surface of the gel, the functional integrity of the tissue was better preserved and the EVC migration started after 24-48 h of culture. Two morphologically different types of cells were seen in the migrating population and have been characterized by immunochemistry using lectin binding and different antibodies (gangliosides, human placental lactogen-hPL, plasminogen activator inhibitor). This model seems to offer a method additional to cell culture for studying the origin, behaviour and markers of EVC.