Metallothionein induction by bismuth in neonatal rat primary astrocyte cultures

Metallothionein (MT) proteins and mRNA levels were determined following exposure of neonatal rat primary astrocyte cultures to bismuth. MT mRNA were probed on Northern blots with [α-³²P]dCTP labeled synthetic cDNA probes specific for rat MT-I and MT-II mRNA. The probes for MT-I and MT-II mRNA hybridize to a single mRNA with a size appropriate for MT, approxmiately 550 and 450 base pairs for MT-I and MT-II, respectively. Expression of MT-I and MT-II mRNA in astrocyte monolayers exposed to 2 and 10 μM bismuth for 6 h was increased in a dose-dependent manner over MT-I and MT-II mRNA levels in control cells. Western blot analysis revealed a time-dependent increase in MT protein synthesis through 72 h of exposure to bismuth (2-10 μM). Consistent with the bismuth-induced increase in MTs at the mRNA and protein levels, a time- (24-72 h) and dose-dependent (2-10 μM) increase in astrocytic MT-immunoreactivity was noted.