Formaldehyde releases calcium from intracellular stores in untransfected HEK293t cells.

<p>A) HEK293t cells were patch-clamped at—60 mV, voltage ramps were applied at an interval of 5 seconds. The currents at ±60 mV of these voltage ramps are displayed; exposure to formaldehyde did not change transmembrane currents (n = 9). B) The steady-state current-voltage relationships 30 s before (open symbols) and during (closed symbols) exposure to formaldehyde are not significantly different (n = 12). C) Calcium transients evoked by formaldehyde 40 mM in HEK293t cells (n = 235) are similar in absence and presence of extracellular calcium, indicating an intracellular release and explaining the lack of a detectable transmembrane current. D) Calcium transients evoked by formaldehyde 40 mM are decreased after exposure to Thapsigargin 5 μM. Formaldehyde responses recovered after replenishing intracellular calcium stores (n = 111). Note the slight delay in calcium clearance due to the application of Thapsigargin, indicating a slow calcium efflux out of the stores when SERCA is inhibited.