Effect of lead on intracellular free calcium ion concentration in a presynaptic neuronal model: 19F-NMR study of NG108-15 cells.

The intracellular free calcium ion concentration ([Ca2+]i) of the neuroblastoma x glioma hybrid cell line, NG108-15, was measured using the 19F-nuclear magnetic resonance divalent cation indicator, 1,2-bis(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetra-acetic acid (5F-BAPTA). The basal [Ca2+]i was measured to be 106 +/- 14 nM. Treatment with 5 microM lead (Pb) for 2 h produced a 2-fold increase in [Ca2+]i to 200 +/- 24 nM and a measurable intracellular free Pb2+ concentration ([Pb2+]i) of 30 +/- 10 pM. Intracellular free Zn2+ concentrations ([Zn2+]i) were also observed in the presence of Pb. This represents the first direct demonstration that Pb elevates the [Ca2+]i in neurons, thus providing evidence for a role of [Ca2+]i in mediating the neurotoxicity of Pb.