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Calcium fluxes in human trophoblast (BeWo) cells: Calcium channels, calcium‐ATPase, and sodium‐calcium exchanger expression
Author(s) -
Moreau Robert,
Simoneau Lucie,
Lafond Julie
Publication year - 2003
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.10247
Subject(s) - biology , plasma membrane ca2+ atpase , calcium , sodium calcium exchanger , microbiology and biotechnology , calcium in biology , homeostasis , gene isoform , ion transporter , medicine , atpase , endocrinology , intracellular , biochemistry , enzyme , membrane , gene
Although placental transfer of maternal calcium (Ca 2+ ) is a crucial process for fetal development, the biochemical mechanisms are poorly understood. In the current study, we have investigated the characteristics of Ca 2+ fluxes in relation with cell Ca 2+ homeostasis in the human placental trophoblast cell line BeWo. Time‐courses of Ca 2+ uptake by BeWo cells displayed rapid initial entry (initial velocity (V i ) of 3.42 ± 0.35 nmol/mg protein/min) and subsequent establishment of a plateau. Ca 2+ efflux studies with 45 Ca 2+ ‐loaded cells also showed rapid declined of cell‐associated 45 Ca 2+ with a V i of efflux (Ve i ) of 3.30 ± 0.08 nmol/mg protein/min. Further identification of membrane gates for Ca 2+ entry in BeWo cells was carried out. Expression of Ca 2+ transporter/channel CaT1 and L‐type α 1S subunit was showed by RT‐PCR. However, mRNA for CaT2 channel and L‐type α 1C and α 1D subunits were not revealed. Membrane systems responsible for intracellular Ca 2+ extrusion from BeWo cells were also investigated. Plasma membrane Ca 2+ ‐ATPases (PMCA) and Na/Ca exchangers (NCX) were detected by Western blot in BeWo cells. Expression of specific isoforms of PMCA and NCX was further investigated by RT‐PCR. Messenger RNAs of four isoforms of PMCA (PMCA 1–4) were detected. The presence of messenger RNAs of two NCX isoforms (NCX1 and NCX3) was observed. Ca 2+ flux studies in Na‐free incubation medium indicated that NCX played a minimal role in the cell Ca 2+ fluxes. Inorganic ions such as cadmium and manganese did not modify the Ca 2+ fluxes, however, barium increased cell‐associated 45 Ca 2+ by, in part, by reducing radiolabel exit. Mol. Reprod. Dev. 64: 189–198, 2003. © 2003 Wiley‐Liss, Inc.