Toxicity testing in vitro. I. The effects of delta 9-tetrahydrocannabinol and aflatoxin B1 on the growth of cultured human fibroblasts.

The acute toxicity of delta 9-tetrahydrocannabinol (delta 9-THC) and aflatoxin B1 to two strains of cultured human fibroblasts has been studied. delta 9-THC had no effect on cell plating efficiency or on the growth of mass cultures at doses of 1 mug/ml (3.18 muM) or less; at 10 mug/ml plating efficiency was reduced by approximately half and at 20 mug/ml colony formation was zero. Aflatoxin B1 reduced plating efficiency at dose levels of 0.1 mug/ml (0.32 muM) and above; in mass clultures it retarded growth at 1 mug/ml and produced complete inhibition at 5 mug/ml. The potential usefulness of cultured human fibroblasts in toxicity testing is discussed and the importance of using normal diploid cells rather than aneuploid permanent lines is emphasized. The limitations of cell cultures in assessing toxicity, and possible solutions to these are considered.