ACIDOSIS-INDUCED METALLOTHIONEIN (MT) MESSENGER-RNA EXPRESSION IN NEONATAL RAT PRIMARY ASTROCYTE CULTURES

Metallothionein (MT) mRNA levels were determined following exposure of neonatal rat primary astrocyte cultures to acidosis. Astrocyte total RNA was probed on northern blots with [alpha(32)P]dCTP-labeled synthet ic cDNA probes specific for rat MT isoform mRNAs. The probe for MT-l m RNA hybridized to a single mRNA with a size appropriate for MT, approx imately 550 nucleotides. MT-I mRNA levels in astrocyte monolayers expo sed to pH 6.5 and 6.0 for 3 or 6 hours were unchanged compared with MT -I mRNA levels in control cultures exposed to pH 7.4. In contrast, 9 h our exposure of astrocytes to pH 6.5 and 6.0 led to a significant incr ease in MT-I mRNA transcripts compared with controls maintained at pH 7.4 (p<0.001 and p<0.02, respectively). A probe for MT-II mRNA that hy bridizes to a single mRNA (450 nucleotides) was also used to determine the effect of acidosis on astrocyte MT-II mRNA transcripts. Although statistical significance was not attained, a similar trend was noted, with a 9 hour exposure to pH of 6.5 and 6.0 resulting in increased ast rocytic expression MT-II mRNA compared with control cells maintained a t pH 7.4. Acidosis was also associated with a pH-dependent increase in astrocytic volume. Accordingly, acidosis is invoked as an added stimu lus to stress factors associated with the induction of astrocytic MT m RNA transcripts. (C) 1998 Intox Press, Inc.