70-KDA SEAT SHOCK PROTEIN EXPRESSION IN CULTURED RAT ASTROCYTES AFTERHYPOXIA - REGULATORY EFFECT OF ALMITRINE

Induction of heat shock proteins (Hsps), especially the 70-kDa family, is well observed in nervous tissues in response to various stressful conditions. By using rat astrocytes in primary culture, the expression of the inducible (Hsp70) and the constitutive (Hsc70) 70-kDa Hsps imm unoreactivity of cells exposed to hypoxic conditions has been investig ated. We observed that exposure of astroglial cells to an hypoxic-norm oxic sequence induces a significant decrease of Hsc70 immunoreactivity . The presence of the heat inducible stress protein Hsp70 is never obs erved in hypoxic cells nor in control. Hsc 70 lowering is associated w ith ultrastructural alterations characterized by mitochondria swelling , formation of vacuoles and accumulation of dense material in the cell cytoplasm. The effects of addition of almitrine to the culture medium before and during hypoxia on Hsps immunoreactivity have been examined . The presence of the drug prevents the decrease of Hsc70 immunoreacti vity induced by hypoxia. Furthermore, some ultrastructural improvement is observed in astroglial cells treated with almitrine suggesting som e protecting role of Hsc70 on cell damage induced by hypoxia.