Response of carp central nervous system to hyperammonemic conditions: an immunocytochemical study of glutamine synthetase (GS), glial fibrillary acidic protein (GFAP) and 70 kDa heat-shock protein (HSP70)

Glutamine synthetase (GS), glial fibrillary acidic protein (GFAP) and 70 kD a heat-shock protein (HSP70) expression were studied in neural tissue of ad ult carp subjected to hyperammonemic conditions using immunocytochemical me thods (immunoblotting, dot blotting, ELISA and immunocytochemistry). Carps were subjected to 1, 2 and 4 mM ammonium acetate for 7, 15, 30 and 60 days since the mortality rate was 100% at 8 mM within 2 days. The mortality rate was 27% at 4 mM. A significant dose-dependent induction of GS was observed in hyperammonemic brains. GS immunoreactivity was located in radial astroc ytes and some ependymal cells. Significant increments of GFAP were observed at 30 days for 1 mM, at 15 and 30 days for 2 mM, and at 30 and 60 days for 4 mM; a heterogeneous response to hyperammonemia was observed in different brain regions. Significant increments in HSP70 were observed in hyperammon emic brain (30 days, 4 mM). The neuronal pattern of HSP70 immunoreactivity under control conditions changed to an ependymal pattern under hyperammonem ic conditions. These results suggest that the main effect of hyperammonemia was GS induction in neural tissue. GFAP induction could be an effect of as troglial activation and HSP70 induction could be related with de novo prote in synthesis. (C) 1999 Elsevier Science B.V. All rights reserved.