Hi Abdullah Abdullah ,

My best guess would be fibrosis as a sign of splenic toxicity. Fibrosis is defined as "the development of fibrous connective tissue as a reparative response to injury or damage". This has come up in other toxicity studies in rodents and is similar to hepatotoxicity.

See: Article Oxidative Stress in the Splenotoxicity of Aniline

Article Chlorpropham-induced splenotoxicity and its recovery in rats