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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
1
|
| pubmed:dateCreated |
1991-9-5
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| pubmed:abstractText |
We have studied the mechanisms involved in calcium (Ca2+) transport through the basal plasma membranes (BPM) of the syncytiotrophoblast cells from full-term human placenta. These purified membranes were enriched 25-fold in Na+/K(+)-adenosine triphosphate (ATPase), 37-fold in [3H] dihydroalprenolol binding sites, and fivefold in alkaline phosphatase activity compared with the placenta homogenates. In the absence of ATP and Mg2+, a basal Ca2+ uptake was observed, which followed Michaelis-Menten kinetics, with a Km Ca2+ of 0.18 +/- 0.05 microM and Vmax of 0.93 +/- 0.11 nmol/mg/min. The addition of Mg2+ to the incubation medium significantly decreased this uptake in a concentration-dependent manner, with a maximal inhibition at 3 mM Mg2+ and above. The Lineweaver-Burk plots of Ca2+ uptake in the absence and in the presence of 1 mM Mg2+ suggest a noncompetitive type of inhibition. Preloading the BPM vesicles with 5 mM Mg2+ had no significant effect on Ca2+ uptake, eliminating the hypothesis of a Ca2+/Mg2+ exchange mechanism. This ATP-independent Ca2+ uptake was not sensitive to 10(-6) M nitrendipine nor to 10(-4) M verapamil. An ATP-dependent Ca2+ transport was also detected in these BPM, whose Km Ca2+ was 0.09 +/- 0.02 microM and Vmax 3.4 +/- 0.2 nmoles/mg/3 min. This Ca2+ transport requires Mg2+, the optimal concentration of Mg2+ being approximately 1 mM. Preincubation of the membrane with 10(-6) M calmodulin strongly enhanced the initial ATP-dependent Ca2+ uptake. Finally, no Na+/Ca2+ exchange process could be demonstrated.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Adenosine Triphosphate,
http://linkedlifedata.com/resource/pubmed/chemical/Alkaline Phosphatase,
http://linkedlifedata.com/resource/pubmed/chemical/Calcium,
http://linkedlifedata.com/resource/pubmed/chemical/Carrier Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Magnesium,
http://linkedlifedata.com/resource/pubmed/chemical/Membrane Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Nitrendipine,
http://linkedlifedata.com/resource/pubmed/chemical/Sodium-Calcium Exchanger,
http://linkedlifedata.com/resource/pubmed/chemical/Sodium-Potassium-Exchanging ATPase,
http://linkedlifedata.com/resource/pubmed/chemical/Verapamil
|
| pubmed:status |
MEDLINE
|
| pubmed:month |
Jul
|
| pubmed:issn |
0021-9541
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| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
148
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
17-23
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| pubmed:dateRevised |
2007-11-15
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| pubmed:meshHeading |
pubmed-meshheading:1650372-Adenosine Triphosphate,
pubmed-meshheading:1650372-Alkaline Phosphatase,
pubmed-meshheading:1650372-Biological Transport,
pubmed-meshheading:1650372-Calcium,
pubmed-meshheading:1650372-Carrier Proteins,
pubmed-meshheading:1650372-Cell Membrane,
pubmed-meshheading:1650372-Epithelial Cells,
pubmed-meshheading:1650372-Epithelium,
pubmed-meshheading:1650372-Female,
pubmed-meshheading:1650372-Humans,
pubmed-meshheading:1650372-Magnesium,
pubmed-meshheading:1650372-Maternal-Fetal Exchange,
pubmed-meshheading:1650372-Membrane Proteins,
pubmed-meshheading:1650372-Nitrendipine,
pubmed-meshheading:1650372-Placenta,
pubmed-meshheading:1650372-Pregnancy,
pubmed-meshheading:1650372-Sodium-Calcium Exchanger,
pubmed-meshheading:1650372-Sodium-Potassium-Exchanging ATPase,
pubmed-meshheading:1650372-Trophoblasts,
pubmed-meshheading:1650372-Verapamil
|
| pubmed:year |
1991
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| pubmed:articleTitle |
Characterization of calcium transport by basal plasma membranes from human placental syncytiotrophoblast.
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| pubmed:affiliation |
Maisonneuve-Rosemont Hospital, Montreal, Quebec, Canada.
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| pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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