Hyperammonemia induces transient GFAP immunoreactivity changes in goldfish spinal cord (Carassius auratus L.)

In this study we have demonstrated that high ammonia concentration in tank water induces changes in the glial fibrillary acidic protein (GFAP) of ependymal cells and radial astrocytes in the goldfish spinal cord. Hyperammonemia was induced by elevating the ammonia concentration in the tank water to 0.88 mM using ammonium chloride; ammonia in control water was less than 0.1 mM. Immunohistochemical methods were used for GFAP and vimentin, and levels were measured at 4, 8, 16, 30, 60, 90 and 120 days. GFAP quantification was made by means of a digital analysis system. The GFAP immunoreactivity was significantly lower at 30 and 60 days of treatment and at 90 days it had returned to control levels. However, no changes in vimentin immunoreactivity were appreciated in any case. GFAP loss was general and was not selective in any specific spinal cord region. To explain this transient generalized loss of GFAP and its posterior recuperation, a possible relation between glutamine synthetase distribution and GFAP changes is discussed.