Variation of superoxide dismutase levels in fetal calf serum

The results of cytogenetic studies and of other experiments based on tissue-culture systems may be influenced by various components of tissue-culture medium and by variations among batches of fetal calf serum used for supplementation of the media. Negative results may be obtained in breakage studies as a consequence of medium components with a protective effect [6]. Attention has been drawn to differences in growth pattern [8] and mitotic indices [11] in lymphocyte cultures set up with different culture media. Variations in the incidence of sister-chromatid exchanges according to differences in media [7] and sera [5] have also been observed. It has been suggested [9] that the failure of some laboratories to detect increases in sister-chromatid exchanges after treatment with the tumor promoter phorbol-myristate-acetate (PMA) may be due to high concentrations of the free-radical-scavenging enzyme superoxide dismutase (SOD) in the sera used and that heat inactivation of the sera may be responsible for these differences. In the following, we report that considerable variation in the SOD content exists between batches of fetal calf serum, up to levels with anticlastogenic effect.