The semiconductor elements arsenic and indium induce apoptosis in rat thymocytes

Indium arsenide and gallium arsenide are important new materials in the semiconductor industry due to their superior electronic properties in comparison with the older silicon-based materials. Animal experiments have shown that exposure to these compounds induces marked alterations in gene expression and immune response. Toxicity to the immune system has frequently been related to T and B cell apoptosis. In the present study we show that the semiconductor elements indium (In) and arsenic (As) are able to induce apoptosis in rat thymocytes in vitro. The results show that exposure to InCl3 (1, 10, or 100 microM) or Na AsO2 (0.01, 0.1, or 1 microM) induced DNA laddering after 6 h of incubation without compromising cell viability. These results were corroborated by flow cytometry analysis of propidium iodide-loaded cells, showing a typical high hypodiploid DNA peak in apoptotic thymocytes. Higher doses of In (1 mM) or As (10-100 microM) induced cell death by necrosis. These data indicate that In and As can induce apoptosis and necrosis in T lymphocytes in a dose-dependent manner, which may be of relevance for their immunotoxicity.