ATP-stimulated Ca2+-activated K+ efflux pathway and differentiation of human placental cytotrophoblast cells

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 282; no. 4; p. 1077
• Main Authors: Clarson, L. H, Roberts, V. H. J, Greenwood, S. L, Elliott, A. C
• Format: Journal Article
• Language: English
• Published: 01.04.2002
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00564.2001

1  Academic Unit of Child Health, University of Manchester, St. Mary's Hospital, Manchester M13 0JH and 2  School of Biological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom 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 µM 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 µM 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 (~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. intermediate calcium-activated potassium channel; calcium entry; human placenta