ORGANIC AND INORGANIC LEAD INHIBIT NEURITE GROWTH IN VERTEBRATE AND INVERTEBRATE NEURONS IN CULTURE

Neurons from brains of chick embryos and pond snails (Lymnaea stagnalis) were cultured for 3 to 4 d in the presence of no toxins, inorganic lead (PbCl2), or organic lead (trielthyl lead chloride). In chick neurons, inorganic lead reduced the percentage of cells that grew neurites (IC50=270μM total lead, approximately 70 nM free Pb2+) but did not reduce the number of neurites per cell or the mean neurite length. Triethyl lead reduced the percentage of cells that grew neuites (IC50=0.24 μM) and the mean neurite length (extrapolated IC50=3.6 μM) but did not reduce the number of neurites per cell. InLymnaea neurons, inorganic lead reduced the percentage of cells that grew neurites (IC50=13 μM total lead; approximately 10 nM free Pb2+). Triethyl lead reduced the percentage of cells that grew neurites (IC50=0.4 μM) and exerted significant toxicity at 0.2 μM. The two forms of lead affected neurite growth in qualitatively different ways, which suggests that their mechansms of action are different.