title: Extremely low frequency electromagnetic field exposure promotes differentiation of pituitary corticotrope-derived AtT20 D16V cells.
abstract: The pituitary corticotrope-derived AtT20 D16V cell line responds to nerve growth factor (NGF) by extending neurite-like processes and differentiating into neurosecretory-like cells. The aim of this work is the study of the effect of extremely low frequency electromagnetic fields (ELF-EMF) at a frequency of 50 Hz on these differentiation activities. To establish whether exposure to the field could influence the molecular biology of the cells, they were exposed to a magnetic flux density of 2 milli-Tesla (mT). Intracellular calcium ([Ca2+]i) and intracellular pH (pHi) were monitored in single exposed AtT20 D16V cells using fluorophores Indo-1 and SNARF for [Ca2+]i and pHi, respectively. Single-cell fluorescence microscopy showed a statistically significant increase in [Ca2+]i followed by a drop in pHi in exposed cells. Both scanning electron microscopy (SEM) and transmission microscopy of exposed AtT20 D16V cells show morphological changes in plasma membrane compared to non-exposed cells; this modification was accompanied by a rearrangement in actin filament distribution and the emergence of properties typical of peptidergic neuronal cells-the appearance of secretory-like granules in the cytosol and the increase of synaptophysin in synaptic vesicles, changes typical of neurosecretory-like cells. Using a monoclonal antibody toward the neurofilament protein NF-200 gave additional evidence that exposed cells were in an early stage of differentiation compared to control. Pre-treatment with 0.3 microM nifedipine, which specifically blocks L-type Ca2+ channels, prevented NF-200 expression in AtT20 D16V exposed cells. The above findings demonstrate that exposure to 50 Hz ELF-EMF is responsible for the premature differentiation in AtT20 D 16 V cells.
authors.affiliation: Consiglio Nazionale delle Ricerche Istituto di Neurobiologia e Medicina Molecolare, Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Lisi
authors.forename: Mario
authors.initials: M
authors.lastname: Ledda
authors.forename: Emanuela
authors.initials: E
authors.lastname: Rosola
authors.forename: Deleana
authors.initials: D
authors.lastname: Pozzi
authors.forename: Enrico
authors.initials: E
authors.lastname: D'Emilia
authors.forename: Livio
authors.initials: L
authors.lastname: Giuliani
authors.forename: Alberto
authors.initials: A
authors.lastname: Foletti
authors.forename: Andrea
authors.initials: A
authors.lastname: Modesti
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Morris
authors.forename: Settimio
authors.initials: S
authors.lastname: Grimaldi
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000528:radiation effects*; D002454:Cell Differentiation / Q000528:radiation effects*; D002478:Cells, Cultured; D004574:Electromagnetic Fields / Q000009:adverse effects*; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D016900:Neurofilament Proteins / Q000378:metabolism / Q000528:radiation effects*; D009543:Nifedipine / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000000981:diagnostic imaging* / Q000378:metabolism; D011859:Radiography; D051381:Rats
chemical_list: D020746:Calcium Channels, L-Type; D016900:Neurofilament Proteins; D009543:Nifedipine; D002118:Calcium