Extracellular potassium influences DNA and protein syntheses and glial fibrillary acidic protein expression in cultured glial cells

✍ Scribed by Karen S. Canady; Francis Ali-Osman; Edwin W. Rubel

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 731 KB
• Volume: 3
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.440030508

✦ Synopsis

Previous reports of increases in glial cell number and expression of glial fibrillary acidic protein (GFAP) in stimulated brain regions or epileptic tissue have implicated a role for increases in extracellular potassium concentration ([EL+],) in glial reactions. We examined the effects of altered [K+l, on DNA and protein syntheses and GFAP expression of cultured glial cells isolated from the posthatch chick brain stem. LK+lo was varied by adding both KCl and NaCl to K+, NaC1-free medium to achieve final [K'] of 1-50 mM. DNA and protein syntheses were measured by incorporation of 311-thymidine and 3H-leucine, respectively, into acid-insoluble material. GFAP expression was measured by a dot-immunoblotting assay. DNA synthesis in glial cells cultured in high (5-50 mM) Kfo was 4540% less than that of cells cultured in low (1-3 mM) K' ,. Protein synthesis per cell was increased 34-44% in cells cultured in high K' as comp;ired to those cultured in low K' . GFAP expression was inversely related to [K+], over the 1-10 mM range. Compared to the baseline of 3 mM K+o, GFAP per cell was increased 65% at 1 mM and decreased 4591 at 10 mM. These data suggest that increases in glial cell number and GFAP immunoreactivity found in sites of increased neuronal activity and in pathological tissues may not be caused solely by persistent increases in [K+l,. Instead, these results suggest that neuronal activity, through the release of K', may have an inhibitory influence on glial proliferation and GFAP expression. In light of work by others implying a relationship between GFAP immunoreactivity and rigdity of astroglial processes together with the data presented here, we suggest that the elevated [Kilo accompanying neuronal activity, by inhibiting GFAP expression, may facilitate the morphological plasticity of glial cells. Conversely, conditions of low [Kilo may contribute to rigidity of astrocytic processes.