title: Ca-ATPase of human syncytiotrophoblast basal plasma membranes.
abstract: In the present work, a Mg(2+)-dependent, Ca(2+)-stimulated ATPase activity was determined and characterized in purified preparations of syncytiotrophoblast basal (fetal facing) plasma membranes, and its characteristics were compared to those of the active Ca(2+)-transport already demonstrated in this tissue. Similar to the active Ca(2+)transport, the Ca-ATPase is Mg(2+)-dependent, is stimulated by calmodulin, and is inhibited by vanadate. The K(m) for Ca(2+)activation is 0.25+/- 0.02microM, a value near to that described for calcium active transport in this tissue. Consequently, the Ca-ATPase activity of human syncytiotrophoblast basal plasma membrane described in this paper could be responsible for the active extrusion of calcium from the syncytiotrophoblast toward the fetal circulation.
authors.affiliation: Instituto Venezolano de Investigaciones Científicas, Centro de Biofísica y Bioquímica, Caracas, Venezuela.
authors.forename: Y C
authors.initials: YC
authors.lastname: Casart
authors.forename: T
authors.initials: T
authors.lastname: Proverbio
authors.forename: R
authors.initials: R
authors.lastname: Marín
authors.forename: F
authors.initials: F
authors.lastname: Proverbio
mesh_terms: D015720:5'-Nucleotidase / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001485:Basement Membrane / Q000201:enzymology*; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002147:Calmodulin / Q000502:physiology; D005260:Female; D005333:Fetus / Q000378:metabolism; D005952:Glucose-6-Phosphatase / Q000378:metabolism; D006801:Humans; D017136:Ion Transport; D007700:Kinetics; D008274:Magnesium / Q000502:physiology; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014327:Trophoblasts / Q000201:enzymology*
chemical_list: D002147:Calmodulin; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase; D005952:Glucose-6-Phosphatase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D002118:Calcium