Stimulation of Ca2+ influx in rat pituitary cells under exposure to a 50 Hz magnetic field.
The effect of exposure of single rat pituitary cells to 50 Hz sine wave magnetic fields of various strengths on the intracellular free Ca2+ concentration ([Ca2+]i), was studied by using dual-emission microfluorimetry, using indo-1 as probe. A 30 min exposure of the cells to vertical 50 microT peak magnetic field triggered a long-lasting increase in [Ca2+]i from a basal value of about 185 +/- 4 nM to 326 +/- 41 nM (S.E.; n = 150). The vertical and horizontal components of the static magnetic field were 57 and 15 microT, respectively. The 50 Hz ambient magnetic field was always below 0.1 microT rms. The effect was observed both at 25 +/- 2 degrees C and at 37 +/- 2 degrees C. Responsive cells, for which [Ca2+]i rose to values above 309 nM, were identified as lactotrophs and represented 29% of the total pituitaries. [Ca2+]i increase, for the most part, was due to Ca2+ influx through voltage-dependent dihydropiridine-sensitive calcium channels inhibited by PN 200-110. However, neither Ca2+ channel blockers nor removal of Ca2+ from the external medium during exposure completely prevented the field-induced [Ca2+]i increase. Additional experiments using an MTT colorimetric assay showed that alteration of Ca2+ homeostasis of lactotrophs was associated with impairment of some mitochondrial processes.
Laboratoire de Physique des Interactions Ondes-Matière, C.N.R.S., E.N.S.C.P.B., Université Bordeaux I, Talence, France.
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D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D017136:Ion Transport; D007700:Kinetics; D008280:Magnetics / Q000009:adverse effects*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D015220:Calcium Channels; D002118:Calcium