title: Metallothionein induction in neonatal rat primary astrocyte cultures protects against methylmercury cytotoxicity.
abstract: Metallothionein (MT) protein and mRNA levels were monitored following exposure of rat neonatal primary astrocyte cultures to methylmercury (MeHg). MT-I and MT-II mRNAs were probed on northern blots with an [alpha-32P]dCTP-labeled synthetic cDNA probe specific for rat MT mRNA. MT-I and MT-II mRNAs were detected in untreated cells, suggesting constitutive MT expression in these cells. The probes hybridize to a single mRNA with a size appropriate for MT, approximately 550 and 350 bp for MT-I and MT-II, respectively. Expression of MT-I and MT-II mRNA in astrocyte monolayers exposed to 2 x 10(-6) M MeHg for 6 h was increased over MT-I and MT-II mRNA levels in controls. Western blot analysis revealed a time-dependent increase in MT protein synthesis through 96 h of exposure to MeHg. Consistent with the constitutive expression of MTs at both the mRNA level and the protein level, we have also demonstrated a time-dependent increase in MT immunoreactivity in astrocytes exposed to MeHg. The cytotoxic effects of MeHg were measured by the rate of astrocytic D-[3H]aspartate uptake. Preexposure of astrocytes to CdCl2, a potent inducer of MTs, completely reversed the inhibitory effect of MeHg on D-[3H]aspartate uptake that occurs in MeHg-treated astrocytes with constitutive MT levels. Associated with CdCl2 treatment was a time-dependent increase in astrocytic MT levels. In summary, astrocytes constitutively express MTs; treatment with MeHg increases astrocytic MT expression, and increased MT levels (by means of CdCl2 pretreatment) attenuate MeHg-induced toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology and Toxicology, Albany Medical College, New York, USA.
authors.forename: L
authors.initials: L
authors.lastname: Rising
authors.forename: D
authors.initials: D
authors.lastname: Vitarella
authors.forename: H K
authors.initials: HK
authors.lastname: Kimelberg
authors.forename: M
authors.initials: M
authors.lastname: Aschner
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001224:Aspartic Acid / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism*; D002104:Cadmium / Q000494:pharmacology; D019256:Cadmium Chloride; D016923:Cell Death; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D003603:Cytotoxins / Q000494:pharmacology*; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002712:Chlorides; D003603:Cytotoxins; D008767:Methylmercury Compounds; D012333:RNA, Messenger; D002104:Cadmium; D001224:Aspartic Acid; D008668:Metallothionein; D019256:Cadmium Chloride