Use of Bromodeoxyuridine For Cell Kinetic Studies In Intact Animals

. A method is described for the use of BUdR for tracing cell proliferation patterns in the intestinal mucosa of intact mice. The method has several distinct advantages over existing methods. Bromodeoxyuridine (BUdR) is a well‐established alternative to tritiated thymidine ([ 3 H]TdR) as a tracer for studying DNA replication. However, its use in cytological as opposed to biochemical studies has been largely confined to examination of metaphase spreads, particularly analysis of sister chromatid exchange (Block, 1982). For this, BUdR incorporation into DNA has been demonstrated using the fluorescent dye Hoechst 33258, together with fluorescence microscopy (Latt, 1973), or Giemsa staining (Perry & Wolf, 1974). Recently, introduction of a monoclonal antibody which recognizes BUdR in single‐stranded DNA (Gratzner, 1982) has enabled BUdR to be used for studying cell cycle kinetics in a manner exactly analogous to the use of [ 3 H]TdR. This has been reported for whole cells in suspension and in monolayer (Dolbeare et al. , 1983; Dean et al. , 1984; Raza et al. , 1984). BUdR included in tissue culture medium is taken up and incorporated into newly synthesized DNA via the same pyrimidine salvage pathway as [ 3 H]TdR (thymidine kinase). A concentration of as little as 10 μm—well below cytotoxic levels (Cerni, 1984)—is sufficient to give readily detectable labelling by immunocytochemistry with a pulse of less than 15 min. the validity of BUdR labelling for cell kinetic studies has been well established in comparisons with other methods by Dolbeare et al. (1983), Dean et al. (1984), and Raza et al. (1984). We describe here the use of BUdR together with an immunocytochemical detection system applied to sections of wax‐embedded tissues, which provides a convenient method of cell cycle analysis in intact animals.