title: ATP-stimulated Ca(2+)-activated K(+) efflux pathway and differentiation of human placental cytotrophoblast cells.
abstract: The aim of this study was to determine whether extracellular ATP ([ATP](o)) stimulated a Ca(2+)-activated K(+) efflux in trophoblast cells that was dependent on extracellular Ca(2+) ([Ca(2+)](o)). Cytotrophoblast cells, isolated from human placenta, were examined following 18 h (relatively undifferentiated) and 66 h (multinucleate cells) of culture. Potassium efflux was measured using (86)Rb as a trace marker. Intracellular Ca(2+) ([Ca(2+)](i)) was examined by microfluorometry using fura 2. [ATP](o) significantly increased (86)Rb efflux to a peak that declined to control (18-h cells) or an elevated plateau (66-h cells) and was inhibited by 100 nM charybdotoxin. Removing [Ca(2+)](o) significantly reduced (86)Rb efflux in both groups as did application of 150 microM GdCl(3). [ATP](o) significantly increased [Ca(2+)](i) in both groups of cells. The response was reduced by removing [Ca(2+)](o) and applying 150 microM GdCl(3). For both (86)Rb efflux and microfluorometry experiments, the response to [ATP](o) was more dependent on [Ca(2+)](o) in 66-h cells compared with 18-h cells (approximately 70% greater). Cytotrophoblast cells exhibit an [ATP](o)-stimulated Ca(2+)-activated K(+) efflux. The dependency of this pathway on [Ca(2+)](o) is greater in the 66-h multinucleate syncytiotrophoblast-like cells, suggesting that the mechanism for Ca(2+) entry may be altered during differentiation of trophoblast cells.
authors.affiliation: Academic Unit of Child Health, University of Manchester, St. Mary's Hospital, Manchester M13 0JH, United Kingdom. lorraine.carson@man.ac.uk
authors.forename: L H
authors.initials: LH
authors.lastname: Clarson
authors.forename: V H J
authors.initials: VH
authors.lastname: Roberts
authors.forename: S L
authors.initials: SL
authors.lastname: Greenwood
authors.forename: A C
authors.initials: AC
authors.lastname: Elliott
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D005260:Female; D005682:Gadolinium / Q000494:pharmacology; D006801:Humans; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D011247:Pregnancy; D012414:Rubidium Radioisotopes; D014327:Trophoblasts / Q000166:cytology* / Q000378:metabolism*
chemical_list: D010455:Peptides; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D012414:Rubidium Radioisotopes; D018999:Charybdotoxin; D001030:Apamin; C064719:iberiotoxin; D000255:Adenosine Triphosphate; D005682:Gadolinium; D011188:Potassium; D002118:Calcium