Abstract: E14 mesencephalic cultures grown 6 days in Neurobasal Medium
containing 10% horse serum consist of differentiated neurons and astroglia. In
these cultures, glutathione and metallothionein-I/II are enriched in astrocytes
and play an important role in heavy metal scavenging and oxidative stress
response. A 24 h exposure to 25 µM Pb, in serum-containing medium, elevated the
glutathione content by more than twofold and increased the metallothionein
I/II-immunolabeled protein band. In contrast, exposure to 3 to 25 µM Pb is
serum-free medium increased Pb uptake by cells 2 to 4-times above the levels
found in 10% serum-containing medium, reduced the glutathione level and
obliterated the metallothionein-I/II protein band. The rapid decrease of
metallothionein-I/II and glutathione levels in serum-free medium implies that
their regulation may depend on a serum factor operative in inducing immediate
early genes. Exposure to 6 µM Pb in serum-free or in B27-supplemented medium
increased the carbonyl content of several protein bands above control levels
indicating that under conditions that curtail metallothionein induction Pb
exposure causes increased oxidative stress.
