Lead exposure increases oxidative stress in serum deprived E14 mesencephalic cultures. Role of metallothionein and glutathione

E14 mesencephalic cultures grown 6 days in Neurobasal Medium containing 10% horse serum consist of differentiated neurons and astroglia. In these cult ures, glutathione and metallothionein-I/II are enriched in astrocytes and p lay an important role in heavy metal scavenging and oxidative stress respon se. A 24 h exposure to 25 mu M Pb, in serum-containing medium, elevated the glutathione content by more than twofold and increased the metallothionein VII-immunolabeled protein band. In contrast, exposure to 3 to 25 mu M Pb i n serum-free medium increased Pb uptake by cells 2 to 4-times above the lev els found in 10% serum-containing medium, reduced the glutathione level and obliterated the metallothionein-I/II protein band. The rapid decrease of m etallothionein-I/II and glutathione levels in serum-free medium implies tha t their regulation may depend on a serum factor operative in inducing immed iate early genes. Exposure to 6 mu M Pb in serum-free or in B27-supplemente d medium increased the carbonyl content of several protein bands above cont rol levels indicating that under conditions that curtail metallothionein in duction Pb exposure causes increased oxidative stress.