This work was supported by the MRC (UK) and MFR (Sweden).
University College London (2003) J Physiol 547P, C50
Oral Communications: Evidence for store-operated Ca2+ entry (SOCE) in human term placental villous fragments
L.H. Clarson*† and T. Powell‡
*Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, †Academic Unit of Child Health, University of Manchester, St Mary's Hospital, Hathersage Road, Manchester M13 0JH, UK and ‡Perinatal Center, Department of Physiology and Pharmacology, Gothenburg University, Gothenburg, SwedenMaintaining [Ca2+]i in the syncytiotrophoblast is necessary for normal placental function and fetal growth. [Ca2+]i homeostasis is a balance between Ca2+ entry and release of Ca2+ from intracellular stores (Berridge et al. 1998). In non-excitable tissue a major pathway for Ca2+ entry is SOCE (Putney, 1997) and this pathway has been implicated in human placenta (Robidoux et al. 2000). In this study we have directly examined stimulation of SOCE in the syncytiotrophoblast of term villous fragments following depletion of intracellular stores with thapsigargin (Tg) in a Ca2+-free buffer. The collection and processing of placental tissue was approved by the Committee for Ethical Research at Gothenburg University, Sweden. Term villous fragments were loaded with fura-2 and superfused with control Tyrode buffer (mM: 135 NaCl, 5 KCl, 1 MgCl2, 1.8 CaCl2, 5.6 glucose, 10 Hepes; pH 7.4 with NaOH). [Ca2+]i was determined by the 340/380 nm ratio. Fragments were exposed to 1 µM Tg in Ca2+-free Tyrode buffer (zero Ca2+ + 1 mM EGTA) followed by control buffer to stimulate SOCE. The effect of 150 µM GdCl3, 200 µM NiCl2 and 200 µM CoCl2 on SOCE was examined by adding blockers to Ca2+-free buffer for 1 min followed by control buffer. Superfusion with control buffer following application of Tg in Ca2+-free buffer caused a rapid increase in fluorescence ratio in 19 out of 22 fragments, suggesting a rapid increase in [Ca2+]i. The increase in [Ca2+]i was reduced significantly by 150 µM GdCl3, 200 µM NiCl2 and 200 µM CoCl2 (see Fig. 1).Figure 1. Effect of 150 µM GdCl3, 200 µM NiCl2 and 200 µM CoCl2 on store depletion-stimulated increase in [Ca2+]i. Data are medians and range. *P < 0.05; **P < 0.01; ***P < 0.001 vs. control. Kruskal-Wallis with Dunn's multiple comparisons test.These data show that the syncytiotrophoblast of human term placenta exhibits a store-operated Ca2+ entry pathway, which is sensitive to GdCl3, NiCl2 and CoCl2. This pathway may be a key mechanism for maintaining [Ca2+]i in syncytiotrophoblast, particularly following agonist stimulation to release Ca2+ from intracellular stores.
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Where applicable, experiments conform with Society ethical requirements.