Sister chromatid exchange in vivo in mice: I. The influence of increasing doses of bromodeoxyuridine.

Bromodeoxyuridine (BrdUrd) pellets weighting either 20, 25, 30, 40, 45, or 53 mg were implanted subcutaneously in strain DBA/2J male mice. Femoral bone marrow cels were analyzed for sister chromatid exchange (SCE) and chromosome aberration frequencies, mitotic induces, and cellular replication kinetics. Small but statistically significant BrdUrd dose-dependent increases of SCEs were observed, whereas chromosome aberrations were induced at low frequencies and occurred independently in Brd Urd dose. The mitotic index remained relatively constant for all doses. A slight inhibition of cellular replication, as manifested by a reduction in third division cells at the 40- and 45-mg doses, was observed. The use of an intense fluorescent light source in the fluorescence-plus-Giemsa technique provided consistently good sister chromatid differentiation at pellet doses substantially lower than those previously used by other investigators.