Increased expression of glial fibrillary acidic protein in the brain of spontaneously hypertensive rats

Astrogliosis, consisting in astroglial proliferation and increased expression of thespecific cytoskeletal protein glial fibrillary acid protein (GFAP) is common in severalsituations of brain damage. Arterial hypertension, which induces cerebrovascularchanges, can cause also brain damage, neurodegeneration and dementia (vasculardementia). This study was designed to assess astroglial reaction in different brainareas (frontal cortex, occipital cortex, hippocampus and striatum) of spontaneouslyhypertensive rats (SHR) in the pre-hypertensive phase (2 months of age), in thedeveloping phase of hypertension (4 months of age) and in established hypertension(6 months of age). SHR were compared to age-matched normotensive Wistar-Kyoto(WKY) rats. Analysis included reverse transcription-polymerase chain reaction (RT-PCR) of GFAP mRNA, GFAP immunochemistry (Western blot analysis) andimmunohistochemistry. A significant increase of GFAP mRNA and an increase ofGFAP immunoreactivity were noticeable in different brain areas of SHR compared tonormotensive WKY rats at 6, but not at 2 or 4 months of age. Immunohistochemistryrevealed a numerical augmentation (hyperplasia) and an increase in size (hypertrophy)of GFAP-immunoreactive astrocytes in frontal cortex, occipital cortex and striatum ofSHR. In the hippocampus of SHR only a numerical increase of GFAP-immunoreactiveastrocytes was found. These finding demonstrating the occurrence ofastrogliosis in the brain of SHR with established hypertension suggest thathypertension induces a condition of brain suffering enough to increase biosynthesisand expression of GFAP similarly as reported in several neurodegenerative disorders and in brain ischemia.