Toxicity of the Immune Suppressant Cyclosporin A in the Rat

The study investigated the effects of Cyclosporin A (Cy A) on adult Sprague-Dawley rats over 21 days, revealing significant toxicity. Administered at 100 mg/kg/24 hr, Cy A caused behavioral changes, including fits, and resulted in the death of 2 rats, with a third euthanized due to severe symptoms. Continuous hair loss was observed. Biochemical changes included decreased serum protein, albumin, and aspartate aminotransferase, with increased alkaline phosphatase and bilirubin. Liver examination showed moderate fatty changes, while kidney analysis revealed proximal tubular cell vacuolation and necrosis. Cy A also induced lymphopenia, increased neutrophils and monocytes, and reduced bone marrow cellularity. The thymus and spleen showed significant lymphocyte depletion, indicating severe immunosuppression.