Indium arsenide and gallium arsenide are important new materials in th
e semiconductor industry due to their superior electronic properties i
n comparison with the older silicon-based materials. Animal experiment
s have shown that exposure to these compounds induces marked alteratio
ns in gene expression and immune response. Toxicity to the immune syst
em has frequently been related to T and B cell apoptosis. In the prese
nt study we show that the semiconductor elements indium (In) and arsen
ic (As) are able to induce apoptosis in rat thymocytes in vitro. The r
esults show that exposure to InCl3 (1, 10, or 100 mu M) or Na AsO2 (0.
01, 0.1, or 1 mu M) induced DNA laddering after 6 h of incubation with
out compromising cell viability. These results were corroborated by fl
ow cytometry analysis of propidium iodide-loaded cells, showing a typi
cal high hypodiploid DNA peak in apoptotic thymocytes. Higher doses of
In (1 mM) or As (10-100 mu M) induced cell death by necrosis. These d
ata indicate that In and As can induce apoptosis and necrosis in T lym
phocytes in a dose-dependent manner, which may be of relevance for the
ir immunotoxicity. (C) 1997 Elsevier Science Ireland Ltd.