Induction of autoimmunity in Brown Norway rats by oral and parenteral administration of sodium silicate

Silica and silicate may disturb immune function such as autoimmunity and tumour immunity. The main objective of this study was to examine the relation between sodium silicate and induction of autoimmunity in genetically susceptible rats. In this study, thirty Brown Norway rats were randomised into four treatment groups, the first and second group receiving 3 mg of sodium silicate (NaSiO(4)) (equivalent to 2 mg silica) in 0.2 mL of normal saline either per oral or subcutaneously, and the third and fourth group (control) receiving 0.2 mL of normal saline (0.9%) through the same corresponding route. A significant number of rats (80%) (P < 0.05) which received sodium silicate by the subcutaneous route showed a high level of serum ANA compared with controls. In the oral, sodium silicate group showed high serum ANA in an insignificant number of rats. Other autoantibodies in both groups (anti-dsDNA, anti-Smith, anti-SSA, anti-SSB) showed gradual increased post exposure, but the numbers of rats with positive titres post exposure was statistically not significant. Silica exposure in rats appears to induce the development of autoimmunity. A longer duration post exposure to silicate seems to be associated with greater risks. Lupus (2009) 18, 413-417.