Apoptosis in mouse fetuses from dams exposed to T-2 toxin at different days of gestation

T-2 toxin (2 mg/kg b.w.) was orally inoculated to pregnant mice at gestatio nal day (GD) 8.5, 9.5, 10.5, 11.5, 12.5, 13.5, 14.5, 15.5 and GD 16.5, resp ectively, and the fetuses were examined 24 hours later. The number and regi on of pyknotic or karyorrhectic cells varied according to inoculation date. In the GD 13.5-subgroup, a moderate to high number of pyknotic or karyorrh ectic neuronal cells were observed in the central nervous system, peri-vent ricular zone to subventricular zone, and pyknosis or karyorrhexis were also observed in a small number of chondroblasts and chondrocytes. In the GD 16 .5-subgroup, a moderate to high number of pyknotic or karyorrhectic cells w ere observed in the thymus and renal subcapsular parenchyma. The nuclei of these pyknotic or karyorrhectic cells were strongly stained by the terminal deoxy nucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end lab eling method widely used for the in situ detection of apoptotic nuclei. In addition, a few fetuses from darns which were given T-2 toxin at GD 13.5 or GD 14.5 and killed at GD 17.5 showed skeletal abnormalities such as wavy r ibs and short scapula. From the present findings and the well known fact th at T-2 toxin readily crosses the rat placenta, it seems that T-2 toxin-indu ced apoptosis in the developing mouse fetuses might be a direct effect of T -2 toxin on fetuses.