Detection of thymocytes apoptosis in mice induced by organochlorine pesticides methoxychlor

The thymus has long been known to be vulnerable to atrophy when exposed to variety of stimuli, including hormones, immunosuppressive pharmaceuticals, and environmental chemicals. The organochlorine pesticide methoxychlor (MXC) is an immunosuppressive agent thought to affect thymic atrophy by inducing apoptosis of thymocyte T cells. We sought to develop an experimental protocol to detect in vivo thymocyte apoptosis induced by MXC in Balb/c mice. We treated the mice with 150-400 mg/kg MXC. We then measured thymus weight, cell counts, caspase activity (3/7, 8, and 9), annexin V labeling of phosphatidylserine (PS) and DNA fragmentation. In MXC-treated mice we observed decreases in thymus weight and cell counts and increases in caspase activity (3/7, 8, and 9), annexin V PS labeling and DNA fragmentation. These results suggest that MXC induces thymic atrophy caused by thymocyte apoptosis, and that our protocol may be useful for detecting in vivo thymocyte apoptosis induced by environmental chemicals in short-time.