Comparison of bromodeoxyuridine labeling indices of smears and sections from mouse NR-S1 tumor

Bromodeoxyuridine (BrdU) labeling indices (LIs) of smears and sections from mouse NR-S1 tumor were labeled in vivo or in vitro and compared to confirm the reliability of smears labeled in vitro. In vivo labeling was carried out by administering 40 mg/kg 5-bromo-2'-deoxyuridine while in vitro labeling was performed by incubating the tumor specimens in RPMI 1640 culture medium containing 200 microM 5-bromo-2'-deoxyuridine under 3 atmospheres. BrdU LIs of sections labeled in vitro (9.49 +/- 0.16) showed lower values than those labeled in vivo (14.95 +/- 0.36). BrdU LIs of smears labeled in vitro (9.87 +/- 0.23) also showed lower values than those labeled in vivo (14.83 +/- 0.49). However, the BrdU LIs of smears were similar to those of sections labeled in vivo and in vitro. In vitro BrdU immunochemistry in smears seems useful for evaluating the biological properties of tumor tissues.