Sodium Citrate as a Substitute for Fetal Calf Serum in the Micronucleus Test

The micronucleus test developed recently by Schmid and coworkers (Boller and Schmid 1970, Ledebur and Schmid 1973, Schmid 1976) is a rapid, convenient, and sensitive procedure for the detection of induced chromosome aberrations in vivo. It is now widely used for evaluating the mutagenic potential of drugs and other chemicals. The test involves the demonstration of micronuclei which result from lagging of acentric chromosome fragments or even of whole chromosomes during mitosis due to spindle disruption in the anucleate young erythrocytes of bone marrow smears (for details see Schmid 1976). Success or failure of the technique largely depends on the quality of the smear. Cell clumping and cell damage render the smear valueless. Schmid (1976) recommends the use of fetal calf serum for preparing the best smears. However, as he also noted, fetal calf serum is very expensive. Moreover it is not readily available in certain countries, particularly developing ones. It is not easy to procure heat inactivated human AB serum either, which Schmid has suggested as a good substitute for fetal calf serum. Difficulty in obtaining these important elements of the procedure is overcome to a great extent by the brief use of 1% sodium citrate solution at 20-25 C as a substitute for fetal calf serum.