Uptake of Cd and Pb in cerebellar granule neurons measured by fluorescent dyes. (A) Confocal microscopy images of Cd (a, b) and Pb (c, d) uptake by cerebellar granule cells preloaded with the divalent metal-sensitive dye Oregon Green. In (a) and (c), neurons were bathed in a physiological saline. In (b) they have been superfused with a solution containing 0 Ca, 30 mM KCl and 100 μM Cd Cl2, which caused the dye fluorescence to increase significantly. In (d), external solution contained 0 Ca and Pb 15 μM, which permeates through the neuron membrane even in the absence of a depolarizing stimulus and also caused an increase in the dye fluorescence. . (B) Real-time recording of the influx of Cd and Pb in Fura-2 loaded cerebellar granule neuron and the effect of membrane depolarization. Cells were treated with the metals in nominal Ca-free solution. From left to right: time course of the fluorescence ratio, , following application of 50 μM Cd and membrane depolarization (25 mM KCl) and application of 15–50 μM Pb in resting conditions and increasing depolarizations (25 and 75 mM KCl). (C) Summary of the results obtained in basal and in depolarizing solutions (25 and 75 mM KCl) with different doses of Pb. The time course of R(t) was approximated by a straight line and the slope dR/dt was calculated in each case, as a measure of Pb influx. Data are mean in 4 experiments and *indicates significantly different from basal (no depolarization) for each dose of Pb .
