Thapsigargin blocks electromagnetic field-elicited intracellular Ca²⁺ increase in HEK 293 cells

Biological effects of electromagnetic fields (EMFs) have previously been identified for cellular proliferation and changes in expression and conduction of diverse types of ion channels. The major effect elicited by EMFs seems to be directed toward Ca²⁺ homeostasis. This is particularly remarkable since Ca²⁺ acts as a central modulator in various signaling pathways, including, but not limited to, cell differentiation and survival. Despite this, the mechanisms underlying this modulation have yet to be unraveled. Here, we assessed the effect of EMFs on intracellular [Ca²⁺ ], by exposing HEK 293 cells to both radio-frequency electromagnetic fields (RF-EMFs) and static magnetic fields (SMFs). We detected a constant and significant increase in [Ca²⁺ ] subsequent to exposure to both types of fields. Strikingly, the increase was nulled by administration of 10 μM Thapsigargin, a blocker of sarco/endoplasmic reticulum Ca²⁺ -ATPases (SERCAs), indicating the involvement of the endoplasmic reticulum (ER) in EMF-related modulation of Ca²⁺ homeostasis.