Effects of aflatoxin B1 on chicken chondrocytes in culture

In vitro effects of aflatoxin B1 on DNA and proteoglycan synthesis were assessed by measuring tritiated thymidine and radiosulfate incorporation by chicken chondrocyte cultures. Chondrocytes were harvested from the growth-plate cartilage of a 35-day-old chicken, cultured in triplicate, and treated with 0, 1, 5, 10, or 25 micrograms aflatoxin B1/ml of culture medium. The cultures were then spiked separately with [3H]thymidine or [35S]sulfate. After the cells, matrix, and medium were harvested, radioactivity was measured by a scintillation counter. Aflatoxin B1 resulted in a dose-dependent inhibition of DNA synthesis, as measured by tritiated thymidine incorporation by chicken chondrocytes: 54.6%, 30.9%, 25.9%, and 5.9% of control in cultures treated with 1, 5, 10, and 25 micrograms aflatoxin B1/ml of culture medium, respectively (P < 0.05). Sulfated proteoglycan synthesis, as measured by radiosulfate incorporation in chondrocyte cultures, was decreased in the media and intercellular matrix by all aflatoxin B1 levels. Compared with controls, 21% less (P < 0.05) radiosulfate was incorporated into non-matrix macromolecules of the medium fraction from chondrocytes exposed to 1 microgram aflatoxin B1/ml. However, 5 micrograms aflatoxin B1/ml was necessary to produce a significant decrease in radiosulfate incorporation in proteoglycans of intercellular matrix (34% less than controls). The ratios of the means of radiosulfate incorporation into intercellular macromolecules to the means of tritiated thymidine incorporation indicated that aflatoxin B1 inhibited DNA synthesis more than proteoglycan synthesis.