Effects of ochratoxins A and B on prechondrogenic mesenchymal cells from chick embryo limb buds.

Prechondrogenic mesenchymal cells from the limb buds of 4-day chick embryos were cultured together with either ochratoxin A (OA) or ochratoxin B (OB) for 6 days. Both toxins inhibited the accumulation of cartilage proteoglycans and general protein synthesis in a concentration-related manner. The IC50 was 1.9 microM for OA and 6.2 microM for OB. Incubating the micromass with OA for periods ranging from 2 h up to 6 days did not produce any metabolites, indicating that OA was the proximal toxic compound in these studies. Neither preincubation with OB nor simultaneous exposure to non-toxic concentrations of OB together with various concentrations of OA influenced the toxicity of OA. The data indicate that interference of OA with general protein synthesis, both in vivo and in vitro, is an important mechanism underlying OA-induced embryotoxicity.